Background and Aims The question of which cellular mechanisms determine the variation in leaf size has been addressed mainly in plants with simple leaves. It is addressed here in tomato taking into consideration the expected complexity added by the several lateral appendages composing the compound leaf, the leaflets. Methods Leaf and leaflet areas, epidermal cell number and areas, and endoreduplication (co-)variations were analyzed in Solanum lycopersicum cv. considering heteroblastic series in a wild-type (Wva106) and an antisense mutant, the Pro35S:Slccs52AAS line, and upon drought treatments. All plants were grown in an automated phenotyping platform, PHENOPSIS adapted to host plants grown in 7L pots. Key results Leaf area, leaflet area and cell number increased with leaf rank until reaching a plateau. In contrast, cell area slightly decreased and endoreduplication did not follow any trend. In the transgenic line, leaf area, leaflet areas and cell number of basal leaves were lower than in the wild-type, but higher in upper leaves. Reciprocally, cell area was higher in basal leaves and lower in upper ones. When scaled up at the whole sympodial unit, all these traits did not differ significantly between the transgenic line and the wild-type. In response to drought, leaf area was reduced with a clear dose effect that was also reported for all size-related traits, including endoreduplication. Conclusions These results bring evidence that all leaflets have the same cellular phenotypes than the leaf they belong to. Consistently with results reported for simple leaves, they show that cell number rather than cell size determines the final leaf areas and that endoreduplication can be uncoupled from leaf and cell sizes. Finally, they re-question a whole plant control of cell division and expansion in leaves when the Wva106 and the Pro35S:Slccs52AAS lines are compared.