In order to help breeders in their attempt at improving organoleptic quality of fresh market tomato a QTL mapping experiment was performed, followed by marker-assisted breeding. The detection of QTLs controlling the variation of several fruit quality traits was performed in the progeny of a cross between a cherry tomato chosen for its good flavour and a line with bigger but less tasty fruits. The lines were evaluated for physical, chemical and sensorial traits. QTLs were detected for all the traits and 8 major clusters of QTLs were detected. The favourable alleles for quality traits came from the cherry tomato, showing the potential usefulness of this line for organoleptic quality improvement. On the contrary, this line provided smaller fruits at all the fruit weight QTLs. A marker-assisted selection scheme was thus set up to transfer into elite lines the five regions carrying the most important QTLs for fruit quality. A backcross scheme was optimised taking into account both theoretical aspects and practical constraints. Three recurrent lines were chosen in order to study the effect of genetic background on QTL expression. After three backcrosses and two selfing generations, lines carrying one to five introgressed regions were selected and evaluated. About half of the QTLs appeared to be stable over genetic backgrounds and generations. A positive improvement of quality components was observed, but fruit weight could not be recovered as expected. Several epistatic interactions among QTLs were shown, which limit the possible progress.