Field studies were conducted during three years to determine the vertical (height level) and horizontal (distance from stand edge) distribution of flying Neodiprion sertifer (Geoffroy) males in a non-outbreak population. Sticky traps baited with synthetic female pheromone (25, 35, 75-diprionyl acetate) were used in a mature stand of Scots pine (Pinus sylvestris L.) in Central Europe (southern Bohemia). The vertical distribution was distinct; more males were caught in traps at 9.0–12.5 m height (crown stratum) than in traps at 2.5 or 0.5 m above ground. The horizontal distribution was rather uniform inside the stand, with only small differences between catches near the stand edge (< 30 m) and inside the forest. These data show that the main flight of N. sertifer males in high pine stands takes place at the crown level. Implications for the use of pheromone traps in monitoring programs are discussed.