A multimedia database management system (DBMS) provides a suitable environment for using and managing the multimedia database. Multimedia objects, which can be defined as objects that integrate values of various media, have temporal and spatial relationship. Objects DBMS have provided better capabilities to manage more complex data. Multimedia Query processing is relatively more complex than normal query processing in a traditional context in which only formatted data are considered. The main problem is the heterogeneity of data processed by the multimedia system. Data with different characteristics, such as video and text, are characterized by different storage techniques and different access structures. This article focuses on defining and discussing query processing in multimedia database systems.