CYP1A1 and CYP1A2 exhibit catalytic activity predominantly for the 2-hydroxylation of estradiol, whereas CYP1B1 exhibits catalytic activity predominantly for 4-hydroxylation of estradiol. To understand why CYP1B1 predominantly hydroxylates the 4-position of estradiol, we constructed three-dimensional structures of CYP1A1 and CYP1B1 by homology modeling, using the crystal structure of CYP1A2, and studied the docking mode of estradiol with CYP1A1, CYP1A2, and CYP1B1. The results demonstrated that two particular amino acid residues for each CYP, namely Thr124 and Phe260 of CYP1A2, Ser122 and Phe258 of CYP1A1, and Ala133 and Asn265 of CYP1B1, play an important role in estradiol recognition.