Branch CO efflux of Norway spruce tree [ Picea abies (L.) Karst.] was measured in ten branches at five different whorls during the growing season 2004 (from June till October) in campaigns of 3-4 times per month at the Beskydy Mts., the Czech Republic. Branch CO efflux was measured using a portable infrared gas analyzer (LI-6250, LI-COR, Inc., USA), operating as a closed system. Branch woody-tissue temperature was measured continuously in 10-min intervals for each sample position during the whole experiment period. On the basis of relation between CO efflux rate and woody-tissue temperature, a value of Q and of normalized CO efflux rate (E-CO efflux rate at 10°C) was calculated for each sampled position. Estimated Q values ranged from 2.12 to 2.89, and E ranged from 0.41 to 1.19 μmolCOms. Differences in branch CO efflux were found between orientations, east-side branches presented higher efflux rate than west-side branches. The highest branch CO efflux rate values were measured in August and the lowest in October, which corresponds with woody-tissue temperature and growth processes during these periods. Branch CO efflux was significantly and positively correlated with branch position within canopy and woody-tissue temperature. Branches from the upper whorls showed higher CO efflux activity and seasonal dynamics than branches from the lower whorls. [ABSTRACT FROM AUTHOR]