Distribution of Aspidogaster conchicola Baer, 1827 in the organisms of its hosts Colletopterum spp. from the Chivyrkuiski Gulf of Lake Baikal was investigated. The number of A. conchicola in the organism of Colletopterum spp. was found to decrease along the row pericardial cavity-mantle cavity-gills-kidney. The pericardial cavity of Colletopterum spp. is the most favorable habitat for A. conchicola with 72% of the helminthes parasitizing in it. In the pericardial cavity the largest number (61%) of A. conchicola was found in its posterior part.