Elizabeth has been portrayed by actress Rebecca Herbst since 1997. In 1999, the role brought Herbst the Soap Opera Digest Award for Outstanding Younger Lead Actress, as well as an Emmy Award nomination for Outstanding Younger Actress in 1999 and a nomination for Outstanding Supporting Actress in 2007.

General Hospital writers brought the character of Elizabeth Webber to Port Charles at the age of fourteen. She is the granddaughter of Dr. Steve Hardy, one of General Hospital's original characters, and the daughter of Dr. Jeff Webber. She is said to have lived in Boulder, Colorado with her parents and her older sister, Sarah Webber. While growing up in Boulder, Elizabeth said that she never received as much attention as her sister did and always rebelled and got into trouble. Her parents ended up moving to Russia to work as doctors there, leaving Elizabeth no choice but to move in with her grandmother Audrey Hardy in Port Charles, New York. Elizabeth developed a crush on Lucky Spencer, but Lucky chose to date her sister, Sarah. On Valentine's Day 1998, Elizabeth was raped. Lucky found her, and the Spencer family helped her through her ordeal. Lucky moved in with Liz for a short while before camping out in a boxcar and then moving into his own apartment. As teens, Liz and Lucky fell in love. In April 1999, Liz was grief-stricken when Lucky was presumed dead after his apartment caught fire. In the months ahead, Liz became close friends with Jason Morgan, who helped her deal with the loss of her first love. In 2000, Luke and Laura discovered that Lucky was alive. He had been held captive by Helena Cassadine and brainwashed into believing that he did not love Elizabeth. Lucky pretended to love Elizabeth because he still cared about her happiness, and they became engaged. The wedding was called off after she realized this. Elizabeth moved on and quickly fell in love with and married Ric Lansing. Elizabeth discovers she is pregnant but she miscarries, leading Ric to blame it on his brother, Sonny Corinthos. Elizabeth divorces Ric after she discovers he was planning on stealing Sonny and Carly's unborn child. When Elizabeth is blinded temporarily, she sleeps with Zander Smith, who dies soon after. Ric agrees to raise the child as his own and the couple renew their vows but she divorces him after she notices his obsession with Sonny.

In 2005, Lucky and Elizabeth began their romance again. Elizabeth was now a nurse at General Hospital and had a son, Cameron Webber, fathered by Zander Smith. Before Lucky and Elizabeth married, Elizabeth chose to become a surrogate mother for Jasper and Courtney Jacks. Lucky did not approve and took a break from their relationship. After a car accident, Elizabeth miscarried. Lucky helped her through her pain, and they began a rocky marriage. Elizabeth was kidnapped by Manny Ruiz in 2006, and Jason rescued her once again. In 2006, Lucky became addicted to painkillers and began an affair with Maxie Jones, his pill supplier. Elizabeth discovered Lucky's infidelity, sought comfort from a drunken Jason Morgan who was heart broken from his separation from Sam. Their drunken one night stand resulted in another pregnancy. Lucky, believing the baby was his, went to rehab while he and Elizabeth divorced. A paternity test revealed that Jason fathered her unborn child. Elizabeth kept the truth a secret to protect the child from Jason's dangerous lifestyle and to keep Lucky from suffering devastation that she believed would cause him to relapse. After Lucky completed rehab, Elizabeth remarried him, while still lying about her unborn child.

After Elizabeth committed perjury in Jason's murder trial, she and Ric had a confrontation where she accused him of holding onto his vendetta against Sonny and Jason, and he accused her of being blind to who Jason is. Elizabeth helped Ric with issues regarding his ex-girlfriend, Marianna, who was in the country illegally, and Ric attempted to keep Elizabeth's relationship with Jason a mystery to Anthony Zacchara in order to protect her. However, they are rarely friendly with each other as Elizabeth finally ceased to trust him. In May 2007, Elizabeth gave birth to another son, Jacob Martin Spencer. Elizabeth was supported by Jason when their son Jake was kidnapped. Sam McCall, reeling from having learned that Jason was Jake's father but would not claim him due to Elizabeth not allowing Jason to claim his son, froze when she witnessed Jake being taken. Jason eventually found Jake and brought him back to Elizabeth. Jason found out that Sam had watched his son get kidnapped. Lucky in his jealousy and anger began an affair with Sam McCall as payback. Elizabeth and Lucky divorced again. In November 2007, during the Black and White Ball, Lucky discovered the truth about Jake's paternity and agreed to keep the paternity a secret to protect Jake. After Emily Quartermaine's death and funeral, Jason and Elizabeth began a secret relationship, where they could see each other but Jason was still not allowed to see Jake. They became engaged, but on the same day of their engagement, Michael was shot and Jason decided that his job was too dangerous for Elizabeth and her children, and he called off their relationship. Elizabeth decided to fight to be in Jason's life, but he was adamant that they would not have the life she wanted. Jason invited Elizabeth to go with him to Italy, but after he witnessed the shooting of Sonny's fiancee, Kate Howard, Jason once again realized that he and Elizabeth would never want the same things in life. In November 2008, a mob war began heating up in Port Charles. Lucky asked Jason to agree to send Elizabeth and the boys, along with Sam, to hide in a cabin. During a shootout between Sam and Elizabeth and Russian mobsters, Jake was kidnapped for a second time. He was safely returned after Sam was able to rescue Jake from a bar that exploded. After this close call Elizabeth finally realized that they will never want the same things in life and parted ways for good.

In early 2009, Elizabeth was poisoned by an airborne toxin carried inside a patient. Lucky helped her through the crisis, but the two decided to remain apart. When Lucky begins dating Emily's unknown twin sister Rebecca Shaw, Elizabeth finds herself attracted to Nikolas and the two kiss, as witnessed by Rebecca. Elizabeth attempts to break things off with Nikolas, and after her son Jake is injured, Elizabeth accepts Lucky's proposal to marry. Elizabeth, still attracted to Nikolas, has sex with him, and is almost discovered by both Rebecca and Lucky.

Lucky begins to believe that Elizabeth does not love him and calls off the engagement, and Elizabeth secretly begins a romantic relationship with Nikolas. Rebecca witnesses the two together, but after Nikolas accidentally hits her with his car, she leaves town without revealing the secret. An emotionally invested Elizabeth decides to have sex with Nikolas for a final time, but Lucky is outraged when he sees the two together. A despondent Elizabeth learns she is pregnant, but despite both potential fathers agreeing to stand by her, Elizabeth's mental state deteriorates to the point she checks into a sanitarium. Feeling stronger, she agrees to have a paternity test to determine which brother is the father. The test reveals that the baby is Lucky's, but Nikolas' grandmother Helena switches the results so she and Nikolas can raise a Spencer baby as a Cassadine. On July 19, 2010, Elizabeth gives birth to a baby boy named Aiden Alexi Nikolossovich Cassadine. On July 20, 2010 baby Aiden goes missing from General Hospital. Elizabeth and Nikolas first suspect Helena Cassadine, but she claims she is innocent. On July 22, 2010 a message appears on the television screens. The message shows Franco, and Lucky and Nikolas suspect him of kidnapping Aiden. But before Franco could reveal where he had hidden Aiden, he fell off the building and died. On August 9, Lucky got back Aiden from Karen, then gave him back to Elizabeth and Nikolas.

On August 17, 2010 Elizabeth and the boys move into Wyndemere with Nikolas.