The study of recovery of porosity by equal channel angular extrusion (ECAE) can be important for manufacturers as ECAE makes an inexpensive tool for improvement of the quality of continuous and semi-continuous cast billets of aluminium. alloys prior to manufacturing in forming processes. It has been shown that pores can change their form under shear deformation and be closed under negative hydrostatic pressure if the pressure exceeds some critical level. In this work, this critical pressure level was shown to be dependent on initial pore size and orientation. Samples for ECAE were cast with the defined level of porosity. They were extruded by an ECAE machine with different back-pressures to manipulate the different processing routes. The existence of pores before and after processing was studied using stereo x-radiography. The shape of a pore was approximated by an ellipsoid or sphere, and transformation of that shape due to finite simple shear deformation has been considered by theoretical and experimental methods. The condition of recovery of a pore relevant to its initial size and orientation was obtained.