Bamboo plantations in two locations in eastern Thailand differed in their biomass yield by an order of magnitude as a result of site productivity and plantation management. The biomass yield of Bambusa beecheyana and Dendrocalamus membranaceus was comparable, but the moisture content of culms of B. beecheyana was considerably higher as compared to D. membranaceus. With D. membranaceus, internodes had higher moisture content, as compared to nodes. The moisture content decreased with increasing height along culms with both species, but this gradient was stronger with D. membranaceus. The moisture content of culms of B. beecheyana declined with increasing culm age, indicating that older culms are more suitable for energetic utilization. While general feedstock characteristics of the two species were comparable, the calorific content of D. membranaceus was significantly higher than of B. beecheyana. Primarily the upper sections and nodes of older culms of both species are attractive options as bioenergy feedstock, but plantations established on marginal sites without proper plantation management will result in very low yields.