Flower buds and flowers of Újfehértói fürtös sour cherry trees were hand thinned. The yield efficiency per unit of trunk cross- sectional area (TCSA), of 20% bud and 20% blossom thinned trees significantly increased compare with untreated control. The yield decreased with increasing the severity of thinning. Significant decreases were found between the yield efficiency per unit of TCSA, tree volume and surface area for the hand thinned treatment by 50% and 80% of buds and flowers in compare with untreated control treatment. Fruit weight and diameter increase linearly with increasing the severity of thinning. Fruits from trees thinned at 80% bud had significantly higher soluble solids compare with those thinned at 20% and 50% of buds and flowers and in compare with unthinned control trees. However, fruits from 80% bud thinned trees had significantly higher soluble solids than control and 50% bud and flower thinning.

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