The nematode Cyathostoma (Cyathostoma) microspiculum (Skrjabin, 1915) was found in 37 out of the 491 great cormorant [Phalacrocorax carbo (L.)] individuals from north-eastern Poland (the Vistula Spit, the Vistula Lagoon and the Masurian Lake District) that were examined. The nematode occurred at 7.5% prevalence, 3.6 mean intensity (1-16 intensity range) and 0.27 mean abundance. This is the first Polish record of C. microspiculum and the first properly documented record of the nematode in Europe. Significant age-dependent differences in prevalence and mean intensity were found; the heaviest infection (13.7%; 4) was found in immature birds, followed by that found in chicks (8.1%; 3.7) and mature individuals (4.4%; 3). No significant habitat-dependent differences in the infection parameters were found but, for chicks, the nematode was present exclusively in those found in the breeding colony located on the Vistula Spit. It may be related to their life cycle, probably associated with a marine environment. Morphology and biometry of the C. microspiculum individuals examined are described in detail. The results are compared with data in the literature. Syngamus hexadontus Chin, 1950 is recognized as an older synonym of C. microspiculum.