Dandelion (Taraxacum officinale) of the Asteraceae family is known for its pharmacological effects and has been used in therapy for centuries. Currently extracts of all parts of this plant are used — root, leaves and flowers. The extracts are prepared using various extraction agents that may significantly affect the effectiveness and therapeutic spectrum of the extracts. The aim of this study was to use three different solvents for the preparation of the extracts from dandelion (Taraxacum officinale) leaves and flowers, namely triton X-100 (2 %), nonidet P-40 (2 %) and acetone (30 %). After extraction, the extractants were evaporated and the dried extracts were dissolved in water to obtain a series of solutions of the concentrations: 125, 250, 500 and 1000 µg.ml–1. The biological effects of the extracts were investigated by means of the MTT test of cell viability. Rabbit kidney epithelial cells (RK13) exposed to the extracts for 24 and 48 hours were used as a model cell line. We observed that the acetone extract of dandelion leaves and flowers at lower concentrations caused an increase in the viability of the treated cells in comparison with the control cells which were not exposed to the extracts (P < 0.05). At the same time, we observed a significant effect of the solvent used for the preparation of the dry extracts on the viability of the cells. The residues of the extractants caused a decrease in the cell viability almost to zero, which in fact means the death of the cells. The selection of the correct extractant for the preparation of the extracts is essential regarding the use of extracts in the pharmaceutical or cosmetic industries.