The purpose of this thesis is to draw a first general portrait on the firm level R&D activity in Greece. First the evolution of the distributions of firms undertaking R&D activities in Greece is examined, in respect to their age, size and industry. Afterwards the firms, separated in terms of their persistence in reporting R&D, are investigated for their size and industry distributions. Finally we examine the R&D intensities of the firms according to their relation to the firm size and their regularities indicated by the literature for the manufacturing sector. The data for these examinations come from a firm level panel data, which we constructed with data taken from HELASTAT for all sectors of economic activity and for the period 2001-2008. / --