The present investigation was conducted on a 22- year old Elm plantation established at Wadura campus of SKUAST-Kashmir. Four diameter classes viz., D₁ (5-10cm), D₂ (10-15cm), D₃ (15-20cm) and D₄ (>20cm) were stratified from the plantation and 24 trees (6 from each diameter class) were randomly selected and felled in the year 2015. The growth parameters of the trees increased with increase in the diameter class. The maximum height, dbh, basal area and stem volume were 14.98m, 23.77cm, 0.044m² and 0.400m³, respectively. Biomass per tree of all tree components viz., stem, branches, foliage and roots showed significant increase with increase in the diameter of the trees. The total biomass, carbon stock and carbon dioxide equivalent increased from lower to higher diameter classes. The highest values observed for these parameters were 475.54 kg/tree (fresh), 148.59 kg/tree and 543.82 kg/tree, respectively under D₄ diameter class. The biomass allocation coefficient of branch and root (BAC_b and BAC_r) attained higher values in lower diameter classes. The maximum and minimum values of these coefficients were 0.158 and 0.085; 0.298 and 0.278, respectively under D₁ and D₄ diameter classes. The size of trees did not produce significant effect on the biomass allocation coefficient of foliage (BAC_f). The diameter of the trees produced non-significant difference in the growth efficiency (GE) of different tree components.