The increase in timber volume gained from planting improved Sitka spruce stock has been estimated to be between 21% and 29% at the end of a rotation. This Research Note presents the results of new research designed to investigate the impact of improved Sitka spruce stock on quality characteristics which determine the quantity of green sawlogs in the forest and construction-grade timber in the sawmill. The study was carried out using trees close to rotation age from a trial of improved Sitka spruce at Kershope Forest in Cumbria. A number of characteristics relating to growth rate and timber quality were assessed on the standing trees in the forest and the sawn timber obtained from the trees after felling. The volume of green sawlogs and sawn timber meeting the strength classes C16 and C24 was calculated. Three improved lots with respectively the highest wood density, fastest growth rate and best stem form were compared with a control of unimproved Sitka spruce of Queen Charlotte Island (QCI) origin. The results at both the individual tree and per hectare level showed increased sawn timber volumes from improved planting stock without deterioration in construction grade strength requirements. In the best progeny, increases of up to 130% in both green sawlog volume and sawn timber volumes per hectare were predicted with equivalent mechanical properties to the QCI stock.