Studies of Opisthobranchia diversity in the Eastern Mediterranean Sea are scarce. In the present study Opisthobranchia species collected along the Mediterranean and Aegean coasts of Turkey in 2004 and 2005 were evaluated. Samples were taken from Canakkale Strait and the northern coast of Gelibolu Peninsula in the northern Aegean Sea, and from Bodrum, Bay of Fethiye, Kas, and Adrasan along Turkey's Mediterranean coast. Sampling was carried out by means of scuba diving. In some locations a bottom dredge sampler was used. In all, 321 individuals were collected, representing 30 species from 7 orders. Among the sampled species, 8 are new taxonomical records for Turkish coasts: Trapania lineata. T. maculata, Diaphorodoris papillata, D. luteocincta, Limacia clavigera. Chromodoris elegantula, Hypselodoris orsinii, and Phyllidia flava. Some of these species, however, were previously recorded in photographs from Turkey taken by amateur divers and underwater photographers.