A multiple mark-recapture study was carried out on the males of a population of Operophtera brumata L. in Hungary using pheromone traps in order to estimate the home range and the population size. The number of males caught by traps set up 1 m above ground culminated after half an hour after the twilight and successively decreased. The delay of the first capture of traps set up different heights was about 1 h per 5 m. Decreasing number of males was caught in traps with increasing height. The flight range of one third of marked males was within 10 m after the 2 -3 days period. The population density of males calculated by 3 estimators of open populations were 4,800-7,200 individuals per hectare.