The distribution of recent photosynthates in 1-, 2-, 3-, and 4-year-old saplings of two hybrid poplar clones (Populus balsamifera × deltoides ‘Northwest’ and P. deltoides × petrowskyana ‘Walker’) was studied using the carbon dioxide (CO2) pulse-labeling technique in summer 2005. The distribution of recent photosynthates was similar between the two clones that were 1, 2, and 3 years old. In the 4-year-old saplings, however, considerable variations in the distribution of recent photosynthates were observed between the two clones. Northwest assimilated 80% more new photosynthates than Walker in the same time period. These results indicate that the distribution of photosynthates was different between the two clones by the fourth year of growth and that Northwest might have an advantage for establishing plantations for biomass production or soil carbon sequestration because of its high growth potential and its ability to allocate more photosynthates to the roots to allow greater exploitation of the belowground resources.