Tetrakis-5,10,15,20-(4-carboxyphenyl)porphyrine (TCPP) was position-selectively introduced into a diblock copolymer film of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) with a sea-island microphase structure. By immersing the PSb-P4VP film into a solution of TCPP/methanol, TCPP was introduced into the island parts comprising P4VP phase. The morphology of the island parts depended on the immersion time and TCPP concentration. A schematic model for the morphological change caused by the phase-selective introduction of TCPP was proposed. (c) 2006 Wiley Periodicals, Inc.