Maintaining biodiversity is of great importance for achieving goal of sustainable development. Nepal has long been doing plantations and manages natural forests to conserve and maintain its biodiversity, but the status of plantation areas in terms of biodiversity has not been assessed yet. This paper attempted to compare biodiversity and the distribution of growing stocks of a plantation area with natural forests. Kushmari plantation area and Banke-Maraha collaborative forest were selected as research sites. Altogether 42 samples were taken to collect the data applying the stratified random sampling. The results showed the biodiversity indices of plantation site were less than that of natural collaborative forests. The values of Shannon-Weaver Biodiversity Index were higher, i.e. 2.52 at Kushmari plantation site than that of 2.34 at Banke-Maraha natural forest. Similarly, values of Simpson Biodiversity Indices were 0.36 at Kushmari plantation site and 0.42 at Banke-Maraha natural forest. Basal area and volume per pole were found to be 0.04m² and 0.651m³ in the plantation site and those for Banke-Maraha collaborative forest were 0.027m² and 0.346 m³ respectively. Thus, the values of biodiversity indices did not show much variation even if there were huge variations in growing stocks in the plantation and natural forests.