The present paper makes use of data obtained from GUS statistical yearbook concerning monthly total number of tourists, including domestic and foreign tourists, and overnight stays provided for them in 16 voivodeships in the period 2004–2014. For the purpose of determining the irregularity in tourist movement in Poland, the following were used in the present paper: the seasonal index of the number of tourist in the period from summer to winter (Slz), and from autumn to spring (Sjw), the number of overnight stays provided for tourist in the period from summer to winter (SNlz) and from autumn to spring (SNjw), and the variability coefficient (W%) throughout the year. Irregularities in the tourist movement is most markedly pronounced in northern voivodeships of Poland, including the Baltic Sea coast and lake regions where the number of tourists in summer is 3–4 times higher than that recorded in winter, and the number of overnight stays provided for tourists is as much as 5–7 times higher. The values of seasonality recorded further into the country are on the decrease, and in the central part of Poland the lowest index values were recorded as for the number of domestic tourists Slz (the quotient of the number of tourist from summer to winter) and overnight stays provided for tourists SNlz (the quotient of the number of overnight stays from summer to winter) – below 2.0, and as for the foreign tourists – below 3.0. In the period from 2004 to 2014 in most voivodeship there is a negative, statistically significant or highly significant trend of the seasonal index of the number of tourists (Slz). On the grounds of the values of the seasonal index of the number of tourists (Slz), both domestic as well as foreign, and the number of overnight stays provided for them (SNlz) and the coefficient of variability (W%) of the number of tourists throughout the year, five areas of different seasonal character of tourist movement were identified: Coastal, Lakeland, Lowland-Metropolitan, Highland and Mountainous area.