Does the size of Populus x canadensis 'Conti 12' change significantly when grown in different planting frames? To answer this question, 10-year-old plantations were studied, growing in five different planting frames, which cover areas of incidence from 6.25 m2 to 12.25 m2. The trial is located in the district of Alberti, province of Buenos Aires, Argentina. The evaluation of stability was carried out on the variables Diameter at breast height (at 1.3 m), Mean Height and Mean Height of the upper quartile. Analysis of variance was carried out using as source of variation the planting frame, the blocks and the interaction between them. The comparison of means was carried out using Tukey's test, and four straight lines were adjusted for each variable studied between values of consecutive areas of incidence, in order to evaluate the intensity of the variation. As results, it was observed that the planting frame was a statistically significant effect factor for the three variables. These variables were less stable at lower incidence areas, and more stable at higher ones, where they also reached their maximum values.