Bank of America Corp. announced today that more than 1 million customers are using the bank's mobile-banking service. "They are definitely a leader in the space," says Gwenn Bézard, senior analyst for the Aite Group, a Boston-based consultancy. Mobile-banking users can check account balances, pay bills, transfer funds and view transactions using cell phones and other mobile devices. BofA's mobile-banking users performed more than 4 million mobile sessions in May, and two-thirds of the active users are younger than 35 years old, according to the Charlotte, N.C.-based bank. Residents of large cities, such as Los Angeles, Atlanta and Washington, D.C., are among the fastest adopters of mobile banking, according to BofA. Bézard suspects the bank's high rate of mobile-banking adoption stems from its "already large base of online banking users." The bank has nearly 25 million online-banking customers, according to BofA, which introduced mobile banking as one of its online-banking services in May 2007. "It's a pool they can tap into to market mobile banking," he says. BofA is "at the forefront of offering this service," contends a BofA spokesperson, who declined to compare BofA's mobile-banking numbers with those of industry competitors.