"Girls always have more fun, so I thought it was a great cause for me," the Girls Gone Bad singer, 20 told PEOPLE after a performance Wednesday night at Chicago's Vision nightclub.
With her charity, The Believe Foundation, Rihanna and Island Def Jam, "got together with a local foundation in three cities and Escada and [the label's fragrance] Moon Sparkle" to sponsor the event, she said. "It was amazing."
The next "Girls Night Out" concerts are scheduled for March 28 at San Francisco's Ruby Skye and April 9 at New York City's HighLine Ballroom.
Autographs for KidsHaving first performed on stage for 40 minutes to a very happy crowd on Wednesday, Rihanna headed upstairs to a private lounge area, where she did a meet-and-greet with children, signing autographs and taking pictures with them.
"When I was young and I would watch television and I would see all the children suffering, I always said when I grow up I want to help," she said by way of explaining why she started The Believe Foundation.
"Not long after I was in the position where I could help. I started to visit all these children's hospitals and I have a soft spot for kids," she says. "I just want to help and make sure they are happy. They can come to a Rihanna concert or have toys or gifts at Christmas."
Future ExpansionShe adds that the foundation "just branched off and we are able to help kids who are less fortunate." According to the foundation's background material, "Believe gives children a chance by providing everything from medical attention for children who can't afford it, school supplies for children in poorly funded public schools, toys for children who are terminally ill and clothes for children in homeless shelters."
Earlier this month, Rihanna also played a major role in a drive that went into helping a New York woman find a donor for a bone-marrow transplant.
"So many people got involved, and it made such a difference," Rihanna said of the outpouring of support for the patient, Lisa Gershowitz-Flynn. "I'm so glad we were able to help give her life and give her to her family."
Moving forward, "I just want to travel all over the world with the kids," the singer says. "As a kid, the thing I hated most was disappointment, so I never want to disappoint kids. I always want to put a smile on their faces. Kids are the future."
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