There are 130,000 strokes in the UK alone each year, causing death or servere disability to those who are affected. Advances in recent times have enabled clot extraction to be undertaken using mechanical thrombectomy devices. In this paper we present a model of such an extraction device, and investigate the value of such modelling in predicting the behaviour of the device under given conditions. A 3-dimensional blood clot simulation associated with a plastic arterial catheter is studied by applying CFD simulations with different size of grid, using the Volume of Fluid (VOF) model. Grid size study shows that the smaller grid size (finer mesh) results in higher accuracy of the output result of the simulation. It is noted that grid independency is achieved when any further increase in the number of cells did not adversely affect the simulation results, the optimum grid size avoided any unnecessary prolonged computational effort required for the simulations with large number of cells. From the results obtained in the grid size study, it can be concluded that mesh 0.3 has reached its asymptotic level. It is believed that it can predict the right clot deformation and blood flow in the device. All the pressures used in this study are able to remove the blood clot. It is found that the higher the pressure applied the faster the removal. Different deformation patterns are also observed when different pressures are applied. It is found that the fastest time to remove the blood clot with the range of pressure used in this work is 0.006 s, when 60 kPa of suction pressure is applied. © 2012 IEEE.