In time of the expansion of information and communication technologies wireless networks take a very important place. Their use is increasing in all segments of society. For this reason, the topic of my thesis is „Wireless networks “which tries to show the concept of wireless networks, their use, advantages and disadvantages and also guidelines for the future. Focus in this thesis is about wireless networks security considering that this is their biggest disadvantage. In the final conclusion we come to the fact that today many companies and institutions as well as a large number of average users are increasingly using devices to wirelessly connect to the Internet primarily due to benefits of wireless networks – mobility, flexibility, simplicity and low costs with the issue of security and data protection as an imperative for each user.