Mobile advertising firm Nokia recently leased 19,437 square feet at 31 St. James Ave. in Boston’s Back Bay.

The five-year lease will increase their presence in the building from the 9,581 square feet that Enpocket, acquired by Nokia in September 2007, already occupies, to a total of 29,018 square feet.

The landlord, Capital Properties, was represented by Tim Lyne and Peter Conlin of CB Richard Ellis. The tenant was represented by John F. Hennessey and Stephen J. Lombardi of GVA Williams.