Historical and contemporary records of 81 vascular plant species of shores from 412 islands in the archipelago of SW Finland are compared to visualise changes in distribution patterns over time, and to identify environmental variables that exert influence on the distribution and on the colonisations and extinctions of species. The environmental variables were measured using GIS. A logistic regression analysis was used to find variables that exert influence on the probability of species occurrences. The total number of species occurrences has increased by 22.7%. On the surveyed islands, frequencies of 60 species have increased or remained unchanged, and those of 21 species have decreased. More species have spread towards less maritime than towards more maritime conditions. Syntheses, including distribution maps, are presented for the species. The decrease in grazing pressure and the eutrophication of the Baltic Sea are probable reasons for the observed changes. Some species have changed their distribution patterns in relation to the environment in unpredictable manners. It is thus concluded that it is worthwhile to analyse the species separately in long term studies when possible.