We report density functional calculations of the lattice instabilities of CdTiO3 and Pb0.5Cd0.5TiO3 supercells. The dominant instabilities in CdTiO3 are against TiO 6 octahedral rotation, as may be expected from its Pnma structure. However, Pb substitution for Cd rapidly supresses this instability in favor of A-site driven ferroelectricity. At the 50% Pb composition, the rotational, rhombohedral ferroelectric and tetragonal (TET) ferroelectric instabilities of the cubic perovskite structure are comparable in energy, and moreover a rather large c/a ratio is found for the TET state. This strongly suggests investigation of the Pb rich part of the (Cd,Pb)TiO3 pseudobinary and minor modifications to it as potential high performance piezoelectric materials.