The paper presents the initial classification of genres and leading themes of pseudonyms of the members of the Polish underground army named Home Army (AK), which were acting in the Wilno (Vilnius) region (now in Lithuania and Belarus) during the WW II. The author underlines their masking and, aspecially, expressive functions. The attention is paid mostly to the patrionyms, nobilonyms, dendronyms, zoonyms and pseudonyms of literary origin (e.g. originated from the novels of Henryk Sienkiewicz). The author also observes the influence of local colour on the lexical and morphological form of some analysed pseudonyms (the presence of Lithuanian and Belorussian elements - the echo of the multinational and culturally varied tradition of Polish-Lithuanian state).