The results of regular observations of atmospheric CO₂ mixing ratios, carried out during the period 1996-2006 at two continental sites located in southern Poland, approximately 100 km apart, are presented and discussed. These sites (Kasprowy Wierch, 49^o14’N, 19^o59’E, 1989 m a.s.l. and Kraków, 50^o04’N, 19^o55’E, 220 m a.s.l) are located in two contrasting environments: (i) high-altitude mountainous area, relatively free of anthropogenic influences, and (ii) typical urban environment with numerous local sources of carbon dioxide of anthropogenic origin. The mean annual CO₂ concentration recorded at Kasprowy Wierch increased from 361.8 ppm in 1997 to 382.7 ppm in 2006. The resulting mean annual growth rate (2.14±0.57 ppm year-1) is slightly higher than that derived for the marine CO₂ reference curve (2.02±0.26 ppm year-1), calculated for the latitude band within which Kasprowy Wierch station is located (48.6oN–53.1oN). The CO₂ mixing ratios measured in the urban atmosphere revealed quasi-permanent excess concentration of this gas when compared with the regional reference. The mean concentration of CO₂ in Kraków for the period 2003-06 was ca. 8.5% higher than that recorded at the high-altitude mountain site (Kasprowy Wierch).