The effect of core size on the calculated binding energies of alkali metal cations (Li+, Na+, K+) to methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, and t-butanol are evaluated using G2(MP2,SVP) protocol. The K+ affinities, reported for the first time, were found to be negative if a core size larger than that of neon (2s(2)2p(6)) was used. Given this, we suggest that the 1s(2), 2s(2)2p(6), and 3s(2)3p(6) electrons have to be included in the electron correlation treatment for Li+, Na+ and K+ containing species, respectively. With these core sizes, our G2(MP2,SVP) Li+ and Na+ affinities are in excellent agreement with values obtained from the newly developed G3 protocol. The nature of alkali metal cation-alcohol interaction is also discussed.