Luteolin and chrysin are biologically active compounds belonging to the group of flavonoids, and can be found in various fruits, vegetables, herbs and spices. They bear a number of beneficial properties to the human health due to a wide range of biological effects such as for example antiinflammatory, antiallergic, antimicrobial and antitumor effects. Antitumor effects are attributed to their ability to act on the redox status of the cell. As antioxidants they can reduce the formation of reactive oxygen species (ROS) and thus counteract malignant processes, while as prooxidants they can increase the levels of reactive oxygen species (ROS) that are consequently toxic for the tumor cell. Reactive oxygen species (ROS) are physiological molecules that participate in cellular signaling, but at higher, nonphysological levels they induce oxidative stress. Such disturbance in oxidation-reduction processes balance within the organism, cause a shift in balance in the organism directed towards oxidation. In such a situation the antioxidative defence system is impaired and the free radicals' levels are increased. This all underlies damage of various macromolecules such as for example proteins, lipids and DNA molecules. The role of free radicals has previously been established in the pathogenesis of many diseases, including malignancies. In the presented in vitro study, the effect of luteolin and chrysin were studied on inhibition of tumor cells growth and ROS generation. Given the promising anticancer effect of flavonoids described previously in the literature as well their proven effect and potential in therapy of malignant disease, the aim of this study was to examine the antiproliferative effects of luteolin and chrysin on osteosarcoma (U2OS) and glioblastoma (A125) cell lines. The effects of these compounds on cell viability was examined in a dose-dependent set-up where increasing concentrations from 20, 40, 60, 80 up to 100 μM were used for cell treatment over 24, 48 and 72h. In addition, oxidative stress levels were measured in parallel as well over 24h. The results indicate that luteolin and chrysin effects on the cell viability depend on concentration and time of treatmant. Luteolin and chrysin have shown selective antitumor effects on target tumor cells U2OS and A1235, in comparison with nonmalignant cells HEK293, and the observed antiproliferative effect corelates with formation of ROS. Availability, selective toxicity, and economic cost-effectiveness point to tested flavonoids as potential antitumor compounds in the treatment of osteosarcomas and glioblastomas.