One of the most important characteristic in ornamental plants is flower shape. Genetic manipulation of regulators of floral organ identity is a possible strategy to modify flower shape. The key role in this process is played by plant MADS-box transcription factors. In this work, two transgenic lines of Nicotiana tabacum plants were analyzed after ectopic expression of three chrysanthemum MADS-box genes: CDM86 and CDM115 (B-class), CDM37 (C-class). Plants of both analyzed lines bloomed earlier and were shorter, formed fewer flowers and seeds weight was significantly reduced in comparison with the control. The calyx was palely colored. The petals had signs of stamens. The stamens formed less pollen and often were shorter than the pistil. Instead of the usual ovary it was an elongated tubular structure, in the middle of which colorless ovules formed. Also number of ovules and their fertility were reduced, which resulted from a lowered seed weight of capsule compared to the control. In conclusion we want to analyze expression of tobacco MADS genes in flower organs of transgenic lines in comparison with the control for a more complete understanding of changes in flower of transgenic plants studied.