Cyclooxygenase is key enzyme in the prostaglandin synthesis. It exists in two isoforms, which have distinct roles in the organism. Cyclooxygenase-2 (COX-2) participates in the pathophysiology of inflammation. Differences in the molecular structure of cyclooxygenases allowed to develop drug that selectively inhibit that isoform. Recently, selective inhibitors of COX-2 were introduced into therapy, providing new opportunities to the treatment of inflammation.