In this diploma thesis I deal with possibilities and conditions of increasing the competition abilities of companies by social networks. In the theoretical part I target essence and history of formation of social networks. I also looked at basic principles of their behaviour and discribed their sources of income. In the practical part I used various statistics of popularity and I chose social networks which can offer the highest increase of share at the market to companies which are interested. Consecutively I created analysis of penetration of chosen social networks to czech bussiness environment and I gave an objective account on this issue using case studies of the companies. At the end I suggested principles for successful managing of s...