The article focuses on the description of the Polish modal expressions trzeba, należy, nie trzeba, nie należy and their Czech counterparts, based on the material of InterCorp. The most frequently used Czech counterparts of these expressions were found to be: muset, být třeba, mít. In the second part of the article, are-conceptualization was undertaken of należy and trzeba and their most frequent Czech counterparts (muset, být třeba, mít). Semantic asymmetry was present, but the same Polish expressions were found amongst the most frequent re-cycled counterparts. The article shows the importance of confrontative research for translation and glottodidactics.