Biomass from short rotation poplar plantations presents a good alternative as a material for energy production, either as a substitute or as an addition to fossil fuels. This research presents the investigation of the potential of the Serbian forestry’s most commonly used clones (a) Populus × euramericana cl. I-214 and (b) Populus × euramericana cl. „Pannonia“ for the production of biomass for energy in different plant density plantations (2500, 3333, 5000 and 10000 plants ha^-1) on the marginal soil for the poplar production. Measured parameters included (a) diameter at breast height, (b); tree height, (c) wood biomass per unit of the area, (d) potentially produced energy per unit of the area, (e) individual tree volume and (f) wood volume per unit of the area. Obtained results indicated significant influence of the plant density on the investigated parameters, while there was no effect of the selected clone or clone x plant density interactio. Such results can be explained by the site conditions and production cycle duration.