New cationic fluorocarbon surfactants 1H,1H,2H,2H-perfluorooctylpyridinium chloride (HFOPC) and 1H,1H,2H,2H-perfluorodecylpyridinium chloride (HFDePC), are synthesized and their emc’s have been determined by the conductivity method. HFOPC-DPC (dodecylpyridinium chloride) and HFDePC-CTAC (cetyltrimethylammonium chloride) mixed systems were investigated from the viewpoint of micellar miscibility. The mutual solubilities of fluorocarbon and hydrocarbon in the micellar phase are predicted by the group contribution method. One can estimate the micellar pseudophase separation regions by using the molecular structure data and the group interaction parameters and predict the alkyl chain length dependence of immiscibility without additional parameters.