The article discusses the occurrence of difficulties which is unavoidable on the way to the target language. Hence, in the theoretical part, we will deal with the basic assumptions of Contrastive Analysis (CA), Error Analysis (EA), Interlanguage, competence and various sources of errors.
In the following paper we will concentrate on the analysis of errors which might occur during the learning process. More specifically, we will pay attention to the problems faced by Polish learners of English. The analysis will be based on both written and spoken corpus – that is PELCRA, where one can identify various erroneous examples made by L2 learners.