"They were really surprised," said Monique Matthews, whose daughter, 12-year-old Tamera, had her picture taken with the entertainment phenom and got to attend Sunday's concert, the last of three at the MGM Grand Garden.
Cyrus spent 90 minutes visiting with stricken children, signing autographs, posing for photographs and chatting.
"She lifted spirits. It's so nice to see famous people help the kids," Matthews said.
"She's really sweet," said Tamera Matthews, who needed a boost after eight months in the ward. "Some kids were too sick so she went to see them."
Cyrus' visit made a difficult weekend more bearable for Tamera's mother.
"I found out Saturday that she has relapsed," said Matthews, who also learned that same day that Tamera had been invited to the concert. Tamera wasn't told about her setback until Monday.
"I didn't want to say anything until afterward," said the mother of three.
When Tamera heard the prognosis from her mother, "she told me, 'At least I got to meet Hannah Montana.' "