Two different theoretical methods have been used to complete a calculation of polarizability in the thallium 6p(1/2), 7s, and 7p(1/2) states. The predictions of the two methods agree to within 1% for the 6p(1/2) and 7s states and 2% for the 7p(1/2) state. We find that the theoretical expression for the 6p(1/2)-7s transition polarizability difference Delta alpha(0) is dominated (greater than 90% contribution) by mixing of the 7s state with the 7p(1/2) and 7p(3/2) states. By comparing the theoretical expression to an existing measurement of Delta alpha(0) [Doret et al., Phys. Rev. A 66, 052504 (2002)], highly accurate values for the thallium 7p excited-state lifetimes have been extracted. The scalar polarizability of the 7p(1/2) state is also computed, anticipating an experimental determination of this quantity, which will then enable a high-precision determination of the 6d(j)-7(pj ) transition rates and provide a benchmark test of the two theoretical approaches in the near future. DOI: 10.1103/PhysRevA.87.042502