Recent record of a threatened planorbid gastropod Gyraulus rossmaessleri (Auerswald 1851) in northwestern Bohemia has stimulated further ecological research since this species occurs in the Czech part of the Elbe River basin only in this area. A detailed research of the species's distribution and habitat preferences in northwestern Bohemia were conducted in 2008—2010. Occurrence of G. rossmaessleri was confirmed in the surroundings of Teplice town at 35 out of 123 sites under study. We found that G. rossmaessleri in this area inhabits different types of temporary wetlands and was also often found in small wetlands in spring areas and in small and slowly flowing rivulets. This habitat preference has not been reported so far.