We present a photometric study of three chromospherically active stars with long periods (V340 Gem, SAO 62042 and FI Cnc). The observations were made at the COMU Observatory in 2006 and 2007. We have made initial photometric analyses of V340 Gem and SAO 62042, which are newly discovered RS CVn-type SB1 binaries, and established the photometric variations of FI Cnc, which is a single G8III active star. Photometric rotation periods of these stars were obtained by analyzing their light variations. The light variations, observed over three or more consecutive orbital cycles, were investigated by using spot models with the program SPOT. We also discussed the surface differential rotation coefficient for the primary component of the SB1 binary star SAO 62042 in this study, using our own photometric period together with an orbital period taken from the literature. (C) 2008 Elsevier B.V. All rights reserved.