In the high forests which managing with close-to-nature silvicultural method, the future of forests depends on the stable establishment of saplings planted in the gaps; hence, the current study was done by selection sampling method with the aim of qualitative and quantitative investigation of natural regeneration based on the gap area in two different beech (Fagus orientalis Lipsky) forests: pure beech forest and beech with other species, in three areas of 1.5- 3, 3-5 and 5-10 R, totally amounting to 60 gaps for two different beech types (30 gaps per forest type) in Sourdar Anarestan forest management plan, Mazandaran province, North of Iran. Number of saplings in different gaps was significantly different at 0.01for both forest types. The number of saplings in small and medium area gaps was greater, whereas that of the larger ones was lower. Concerning the mean area of gap with beech forest types, there was significant difference at 0.01.The area of gaps created in the mixed beech stand was more than that in the pure beech forest and according to Duncan's test; maximum gap area was east aspect and then north eastern and west aspects. Also, results showed that as the gap area increased, the number of saplings and their quality decreased for each type. Therefore, maximum the best gap area of 3 to 5 R can be suggested to ensure the future of the planted saplings.