A competition belongs to the main principles of public procurement. The public procurement has to be opened to competition in order to fulfil the main objectives of public procurement – to select a bid most convenient as quality price ratio principle is concerned. The article gives a more detailed analysis of economic subjects as possible public procurement participants. It explores differences in understanding the key concepts – undertaking, consortium, economic activity - from the point of view of both branches of economic regulation. At the same time it offers solutions how to develop competition in public procurement – on one hand through adequate interpretation of the relevant concepts, on the other hand, eventually, by amending the public procurement legal regulation.