The paper approaches an important issue of the phonological similarity of words, relevant for current research in phonotactics, word recognition, production and acquisition, by analyzing the data collected in an experiment in which 30 native speakers of Polish were asked to provide phonologically similar words to 80 nonwords. The study demonstrates that the uncovered patterns of phonological similarity (segment substitutions, deletions and additions, the use of bigrams, trigrams and quadrigrams, noncontiguous sounds and segment metathesis) go beyond the commonly employed concept of neighbourhood density and point to the need to revise the current approaches to phonological similarity of words. It is argued that the experimental results can be attributed to the considerably more complex phonotactic and morphological structure of Polish than English.