Experience over several years has indicated that chemotherapy, even if widely used, does not always remain effective in the therapy of lung tumours and, in addition, is linked to serious side effects. In parallel, some plant polyphenols are known to exert a proapoptotic action on tumour cells while, in contrast, representing anti-cancerogenic anti-oxidants in living organisms. Our studies were aimed at comparing the effects of a polyphenol, quercetin, and cisplatin on cells of various types of lung cancer in in vitro conditions. In these studies we also attempted to define the relationship between the dose and the duration of the activity of the compounds. Cisplatin alone was found to induce only a small reaction in the cells, while in combination with quercetin its anti-proliferative and pro-apoptotic effects were amplified, depending upon the type of tumour, the dose and the duration of the drug’s action.