Communication could be considered an amalgam of language and culture whether we are trying to communicate in our mother tongue or in a foreign language. In each “piece of discourse” (Coşeriu, 1986: 113), we can find a large number of paremias, phraseological expressions (Şodolescu Silvestru, 2002) or phraseological units (Cristea, 2009; Sánchez Martínez, 1990) that have called linguists’, folklorists’, psychologists’ and language teachers’ attention. The importance of phraseological units (UFs) in the spoken or written discourse is obvious, as well as the difficulty of learning how to use them in a foreign language. Phraseological Units have two main features: unity and fixation. However, there is a third one: expressivity that could also be related to them. In this paper, we would be analyzing UFs but, at the same time, we will try to carry out a contrastive analysis of a selection of UFs that express trust / distrust and ease / difficulty. We would try to observe and establish a series of differences and similarities between Spanish and Romanian UFs. We consider that our investigation could provide important information for both Romanian students who study Spanish as a second language as well as for future translators.