Cyclooxygenase plays a pivotal role in the transformation of the arachidonic acid to prostaglandins (PGs) and thromboxane. It is composed of two kinds of enzymes, namely cyclooxygenase 1 (COX-1) and cyclooxygenase 2 (COX- 2). Cyclooxygenase 1 is the constructive enzyme whereas the cyclooxygenase 2 is the inducible enzyme. Inhibiting cyclooxygenase 1 is always associated with some undesirable side-effects, while inhibiting cyclooxygenase 2 can result in therapeutic effect. This has led the researchers to strive for searching the selective inhibitors inhibiting the COX-2 instead of COX-1. It is very well known that pain and inflammation are alleviated through the inhibition of COX-2 inhibitors such as Aspirin, which has resulted in the recent years, in the emergence of a range of COX-2 inhibitors. Moreover, while evaluating the functions of the COX-2 inhibitions, their significant role in treating glaucoma, preventing and suppressing cancer through their inhibitory activity was clearly revealed and many studies further demonstrated that COX-2 is not only related to the inflammation of peripheral tissues but also to the inflammation manifested in the central nervous system. In addition, the nervous disorders also found an effective treatment with the administration of COX-2 inhibitors. The above-mentioned findings delineate the role of the COX-2 inhibitors as promising agents to be exploited in the treatment of many illnesses. This review will elucidate the functions of the COX-2 inhibitors briefly and introduce some common selective inhibitors of COX-2.