This work presents the results of investigation of the main physical characteristic - basic wood density, of two Eastern cottonwood clones P. deltoides Bartr., cl. 457 and cl. 618, aged 4 and 6 years, with two different plant density 5000 plants/ha (2x1 m), and 3330 plants/ha (2x1.5 m). The aim of this investigation was to estimate the influence of plant density, as well as different age, on basic wood density of juvenile wood of Eastern cottonwood. It was found out that the differences in wood densities values for both ages (4 or 6 years) are small and insignificant. Significant differences are obtained only for different sampling heights of analyzed stem (1.3 m, 1/2 H or 3/4 H): increasing of wood density with stem height. Differences of average wood density values between the clones are insignificant.