Abstract. Assessment of plant diversity of the Reserve Forests of the west Himalaya and prioritization of communities for conservation have not been given much attention. Therefore, the study has been conducted in a biodiversity rich Mornaula Reserve Forest between 1500-2200m to analyse the structure, composition of the forest communities including richness of economically important, native, endemic and rare-endangered species, and prioritize communities for conservation. A total of 123 sites were sampled. For each site, habitat characteristics, altitude and dominant species have been given. From the sampled sites, 289 species (37 trees; 37 shrubs; and 215 herbs) and 31 forest communities have been recorded. These recorded values were almost comparable with the studies conducted in sub-tropical, temperate and sub-alpine regions of the west Himalaya. In some cases the values were slightly higher than the reported values. The communities have been prioritized for conservation based on the species richness, nativity, endemism, economically important and rare-endangered species. Among, all the prioritized communities, Rhododendron arboreum community supports maximum species including native, endemic, economically important and rareendangered species. In view of the high socio-economic and conservation values of the identified communities, monitoring of these communities at least for a period of five years and development of appropriate strategy and action plan for the conservation and management have been suggested.