Integrating solar thermal technologies with gas turbine cogeneration plants reduces fuel consumption and consequently results in a considerable reduction in gas emissions. These technologies are expected to play an important role in solving the global environmental and energy problems. The present work provides a detailed investigation of the technical and economic feasibility of integrating a Parabolic Trough Collector (PTC) system with gas turbine cogeneration system. In this regard, different generating capacities of gas turbine and areas of solar collectors have been examined and presented for a hybrid solar gas turbine cogeneration system that produces electricity and process steam at a rate of 81.44 kg/s at 394 degrees C and 45.88 bar. Thermoflex with PEACE simulation software has been used to assess the performance of each proposed integration design option. Optimum solar field size for each considered gas turbine generating capacity (size) has been identified. Also, the reduction in CO2 emissions due to the integration of PTC systems has been calculated as percentage of the CO2 emissions from the conventional system for each gas turbine generating capacity size. The results indicated that hybrid solar gas turbine cogeneration systems with gas turbine generating capacities less than 90 MWe demonstrate a negligible increase in the levelized electricity cost (LEC), which was between 5 US phi and 10 US phi/kWh. It was demonstrated also that integrating a PTC system with a gas turbine cogeneration system of less than 110 MWe generating capacity has more economic feasibility compared to CO2 capturing technologies. (C) 2014 Elsevier Ltd. All rights reserved.