Antenna miniaturization has received increased interest in antenna and related fields due to the desire for small and versatile antennas in radio communication systems. Nowadays, increasing demand for multifunctional systems derive more requirements for small mobile terminals, including cell phones, handheld portable wireless equipment for internet connection, short and long range communication devices, RFIDs (radio frequency identification), and others. Also, small equipment and devices which are used for data transmission and navigation (GPS systems) require small antennas. These applications and continuing growth of wireless devices have persuaded researchers to create smaller and more multifunctional antennas. The small physical size, low cost, broad bandwidth, and good efficiency are desirable features of an integrated antenna. Also, the quality factor (Q) and the radiation loss of the antennas are inversely related to the antenna size. Metamaterial-based antenna designs were developed in the early 1990s which resulted in a significant size miniaturization while maintaining a good radiation performance. In these antennas the dispersion relation and/or the near field boundary conditions are manipulated. In fact, metamaterial antennas opened a way to overcome the restrictive limitation of small antennas. In this thesis, a patch antenna with a central frequency of 2.4 GHz is designed which has been miniaturized significantly by using two different metamaterial structures: Reactive Impedance Surface (RIS) and Composite Right Left Hand (CRLH) structures. Three different antennas are proposed. Two of them have the same CRLH structure, but different numbers of frequency bands. One antenna is double-banded and the other has four bands. The third antenna designed with nine CRLH unit cells, has a different performance in comparison with the other antennas. Key Words: Antenna Miniaturization, Patch antenna, Reactive impedance surface, CRLH.