Since enterprises nowadays are increasingly advanced technologically, their competitiveness depends on service quality and client satisfaction. So the main fields where the enterprises seek solutions are client-oriented services, learning client needs and increasing client satisfaction level. It was caused by consumers' demand of better services, faster information and clients' higher awareness of their rights. The enterprises present on the market changed their strategy. Instead of concentrating on gaining maximum share in the market, they started fighting to keep loyal clients creating the CRM (Customer Relationship Management) concept. The article's aim is to present the essence of the CRM system. It presents key aspects determining effective implementing CRM system in Poland. The example is Polish national telecom operator.