This article presents a study of lemmatisation of flexible multiword expressions in Lithuanian. An approach based on syntactic analysis designed for multiword term lemmatisation was adapted for a broader range of MWEs taken from the Dictionary of Lithuanian Nominal Phrases. In the present analysis, the main lemmatisation errors are identified and some improvements are proposed. It shows that automatic lemmatisation can be improved by taking into account the whole set of grammatical forms for each MWE. It would allow selecting the optimal grammatical form for lemmatisation and identifying some grammatical restrictions.