The telecommunications industry is currently one of the technologically most important and fastest growing sectors of the economy. Over the last two decades, mobile communications have become an integral part of this industry, enabling the formation and growth of national income, increasing corporate and government revenues as well as creating new jobs. For the purpose of this paper, the findings of two consecutive six month long surveys will be presented, measuring the satisfaction levels of users of three mobile phone companies which operate in Greece, as well as the relationship of these findings and the changes of market shares of the three companies. For the collection of the data, questionnaires were used in order to better record the customers’ views on the service overall as well as their satisfaction levels on particular aspects of the service. T he analysis of the results has been based on the multicriteria MUSA method, which is part of the wider category of aggregation–disaggregation approach and is based on the principles of qualitative analysis regression. T he results of the data analysis provide strong indications that the changes in customer’s satisfaction level affect the market share.