The objective of this work is to investigate the impact of the geometric dimensions of parabolic trough collector (PTC) in the optical, energetic and exergetic efficiency. The module of the commercial LS-3 PTC is examined with SOLIDWORKS FLOW SIMULATION in steady-state conditions. Various combinations of reflector widths and receiver diameters are tested. The optical and the thermal performance, as well as the exergetic performance are calculated for all the examined configurations. According to the final results, higher widths demands higher receiver diameter for optimum performance. For inlet temperature equal to 200 °C, the optimum design was find to be 3000 mm width with 42.5 mm receiver diameter, with the focal length to be 1840 mm (this is kept constant in all the cases). The results of this work and the presented methodology can be used as guidelines for the design of optimum PTC in the future.