The article presents results of the econometric modeling of tourist traffic based on time series models with seasonal fluctuations over the 2000-2014 period. The study's subjects were two of the most visited Polish national parks, both by Polish and foreign tourists, i.e. Wolin and Tatra National Park. The study showed that tourism in these parks was relatively stable, the maximum increase in the number of tourists was recorded in July and August, and the biggest decrease in December and January. This demonstrates the strong seasonality of tourism phenomena, conditioned more by the time of year than the location.