Various data have constantly pointed out a low incidence of non-marital unions in Poland (at 1.4-4.9% among all unions). In this paper we demonstrate that these data, coming exclusively from cross-sectional surveys, clearly underestimate the scale of the phenomenon. By exploiting data on partnership histories we show that young Poles have increasingly opted for cohabitation. Consequently, in the years 2004-2006, entries to cohabitation constituted about one third of all first union entries. Consensual unions have traditionally been seen as being more widespread among the lower social strata, but a clear increase in cohabitation has been also been recently observed among groups with higher levels of educational attainment. Although the estimates of cohabitation incidence are far below those observed in Northern and Western Europe, our study suggests that Poland is not as ‘immune’ to the spread of consensual unions as it is commonly believed.