Slurry pumps are extensively used in the hydraulic transportation of fly ash slurries through pipes in thermal power plants. Today, a wide range of slurry pumps are available and the most commonly used pumps are broadly classified into two main categories, namely, positive displacement and centrifugal pumps. These two types of pumps differ considerably in construction as well as in operating principle compared to the conventional pumps. The aim of the present study is to compare the performance characteristics of these two different types of pumps operating with high concentration fly ash slurries. For each type, the performance characteristics have been experimentally evaluated at the rated speed with water as well as with fly ash slurries in the concentration range of 50 to 70% by weight. The pump total head, overall efficiency, and pump input power as a function of the flow rate have been measured. The results obtained from the centrifugal slurry pump performance show that at rated speed, the head and efficiency of the pump decrease with an increase in solid concentration and the effect is strongly dependent on slurry properties. The pump input power also increases monotonically with an increase in solid concentration. In the case of progressive cavity screw pump, pump performance characteristics and behavior were completely different compared to the centrifugal slurry pump. At rated speed, the head developed and the efficiency of the pump improved with an increase in solid concentration for progressive cavity screw pump.