Total energy calculations performed for ScAlO3 perovskite, using the global parametrization method (GPM) in conjunction with the exact muffin-tin orbitals theory, show that the orthorhombic Pbnm structure remains stable relative to the cubic structure for pressures up to 150 GPa. The slightly larger compressibility of AlO6 octahedra relative to the ScO12 polyhedra is reflected in increasing polyhedral volume ratio, VSc/VAl and in a moderate reduction of the orthorhombic distortion with hydrostatic pressure. This observation indicates limitations in the structural analogy between ScAlO3 and the geophysically important MgSiO3 perovskite.