The interest for multimedia database management systems has grown rapidly due to the need for the storage of huge volumes of multimedia data in computer systems. An important building block of a multimedia database system is the query processor, and a query optimizer embedded to the query processor is needed to answer user queries effciently. Query optimization problem is widely studied for conventional database systems, however it is a new research area for multime-dia database systems. Due to the di erences in query processing strategies, query optimization techniques used in multimedia database systems are different from those used in traditional databases. In this thesis, query optimization problem in video database systems is outlined and a query optimization strategy is proposed as a solution to this problem. Reordering algorithms, to be applied on query execution tree, are also described. Finally, the performance results obtained by testing the proposed algorithms are presented.