The changes in the demographic structure of societies are one of the key factors affecting the social and economic life in a modern world. The article tries to identify key demographic changes that affect the demand for health tourism services. It focuses particularly on the situation in Poland, as in this country the worst levels of basic demographic indicators in Europe has been recently observed. Authors utilize the yearly number of spa visitors coming to the Polish health resorts in period 1995-2009. The data were compared with the demographic trends referring to the number of population in 15 age categories, the probability of death, average life expectancy at birth, number of deaths and births per 1000 population. The impact of individual factors was examined by the analysis of correlation between the scale of demand for health tourism services, and the time series on demographic factors. The prediction for the further development of the phenomenon required the use of linear regression and multiple regression. In result of the performed analyses, it is concluded that demographic changes may be a key factor negatively affecting the number of patients coming to Polish spas, and the upward trend observable in recent years in terms of the demand for health tourism in Poland, with a great probability will turn into a downward trend in the forthcoming years.