This paper describes performance modeling and cost assessments for processes to capture CO2 from sub-critical pulverized coal-fired power plants (PC) and Integrated Gasification Combined Cycle (IGCC) units firing sub-bituminous Powder River Basin coal. Oxy- Combustion (OC) and amine scrubbing (MEA) are considered as technology options to capture CO2 from PC plants and the Selexol process to capture CO2 from IGCC plant. Detailed results of the mass and energy balances of the power generation systems and CO2 capture processes were obtained using process simulation software, CHEMCAD. Cost models were developed to estimate the capital cost, the O&M cost, the cost of electricity and the cost of CO2 avoidance for each technology at 533 MWe gross power output. The results from the process simulations show that the OC and MEA processes consume about 32% and 35% of the total gross power output, respectively. The economic analysis reveals that the cost of electricity for the plant with OC is increased by about 60%, with MEA plant by 79% and for the IGCC + Selexol plant by 43%, compared to the PC plant without CO2 capture. The CO2 avoidance cost for a new sub-critical PC+OC plant is $35/ton, compared to $52/ton for the PC+MEA plant and $26/ton for the IGCC + Selexol plant. For PC plants, OC is the most economical option for both new and retrofit options. IGCC with Selexol is economically favorable for new coal power plants. Economics of the OC process can be further improved by (ultra) supercritical power plants and by integrating the oxygen generation unit to improve the overall energy utilization efficiency.