The influence of 'CAB 6P', 'CAB 11E', 'Masto de Montañana' ('MM 9'), 'MaxMa 14', 'MaxMa 97', 'GM 61/1' ('Damil'), 'Colt' and 'Sainte Lucie GF 64' ('SL 64') rootstocks on fruit quality of 'Sunburst' sweet cherry is studied. The experiment was performed in the Ebro Valley (Zaragoza, Spain), on a heavy and calcareous soil. To evaluate the effect of rootstocks, parameters such as fruit size, fresh weight, colour, firmness and some chemical fruit properties (acidity, pH and soluble solid content) have been determined. In addition, the most important sugars present in fruit juice (glucose, fructose and sorbitol), were analyzed by High Performance Liquid Chromatography (HPLC). Significant differences in sugar concentrations, colour parameters, fruit weight and firmness were found among rootstocks. The highest fruit weight and calibre was induced by P cerasus and 'Colt' rootstocks, especially for the high-yielding years. Preliminary results indicate that rootstocks with high total soluble solids in fruits also showed high values for fruit firmness.