'Dictionary of Language Errors' by J. Szwed, published in Vilnius in 1931, is worth linguists' attention, particularly those interested in Polish language used by inhabitants of the Northern Borderlands and experts in lexis of the Interwar period. The dictionary contains authentic language materials excerpted from learners' compositions, press, literature as well as everyday Polish. The handbook written by a Vilnius teacher of Polish completes our knowledge about Polish language used after the Partition period.