The influence of flower or fruit hand-thinning methods on fruit quality was estimated in the experiment conducted from 1997 to 1999, at the commercial orchard near Lublin in Poland. The experiment was carried out on ' Sampion' trees/M.26 planted in a bed system at 1 x 2 x 4 m spacing. The study was a complete randomized block design with a single-tree plot replicated eight times. In 1999, during the vegetative period, the dynamics of fruitlet growth were also observed. Fruitlets on trees subjected to flower thinning towards the end of the flowering period, were characterized as having a fast rate of growth in all separated subperiods. However, the control fruits, despite having quite a fast rate of growth in the first separated subperiod, showed the slowest rate of growth in the following two subperiods. Flower thinning at the pink bud stage, and towards the end of flowering had a beneficial influence on yield of fruit > 70 mm in diameter and mean fruit mass. The control trees gave the smallest yield of fruit > 70 mm in diameter. The control fruits were characterized as having a lower mean fruit mass. Fruits from trees subjected to flower thinning at the pink bud stage had the biggest P and K content, but tended to have the smallest Ca content and the biggest K/Ca ratio. The control fruits had the great Ca content and tended to have the lowest K/Ca ratio.