This article describes the basic principles and approaches used in cellular communications to guarantee protection of voice and data massages, connections, network and system equipment. It is well known that Public Land Mobile Networks (PLMN) needs a higher level of protection than traditional telecommunication networks. The second generation cellular systems as a kind of mobile digital radio systems allow to guarantee the so called information and subscriber security to their users discussed in the paper as secrecy and authentication. In the second generation cellular systems the terms “security” and “protection” (based on the GSM-standard) mean preventing unauthorized use of the system resources and ensuring secrecy of conversations (based on RSA-algorithm) between mobile users. In this aspect, the author describes the following approach to protection and security: authentication; secrecy of transmitted voice and data; secrecy of subscriber; secrecy of equipment; secrecy of connections; and secrecy of signals for command and control. Because in wider sense the term security includes also error protection of information, various standards for coding in cellular systems are described and compared.