AbstractThe vertical and temporal distribution of coarse particulate organic matter (CPOM) larger than 1 mm from 0 to 70 cm depth within the substrate was observed at two different sites along a riffle in the River Morava. Samples of hyporheal sediments were taken by inserting a steel cylinder and a special grab. The amount of CPOM was determined by combustion. The maximum amount of CPOM was found at a depth of 30‐40 cm; lower levels of CPOM were observed in deeper horizons. The average amount of CPOM in 10cm layers (volume 1582.9 cm3) was 232.2 gm−3at station A and 691.3 gm−3at station B. The content of CPOM showed a maximum during the s