Hydroporus tartaricus LeConte, 1850, is restricted to the Nearctic region. In Fennoscandia this name has included the two species H. eugeniae Zaitzev, 1909, and H. nigellus Mannerheim, 1853. Separating characters are given together with notes on the distribution of this species-pair. Lectotypes are designated for H. nigellus Mannerheim, H. geniculatus Thomson, H. longitarsis J. Sahlberg, H. sieversi J. Sahlberg, H. subseriatus J. Sahlberg and H. afflatus Scholz. The last one is placed in synonymy with H. eugeniae Zaitzev.