Lower montane rainforest and upper montane forest on the slopes and summit of Gunung Sinombayuga, Dumoga Bone National Park, North Sulawesi, were described by general botanical collection and quantitative sampling. The lower montane forest was dominated by the families Fagaceae, Myrtaceae, Icacinaceae and Escalloniaceae. The upper montane forest, dominated by Fagaceae and Cunoniaceae, represented 75-year-old coppice regeneration. It was less diverse than the lower montane forest and lower in stature, with a smaller basal area per hectare and a higher proportion of multi-stemmed trees. The tree flora of the montane forest is poorly known, and rich in undescribed species.