Univ Toronto, Dept Phys, Toronto, ON M56 1A7, Canada
; CCAST, World Lab, Beijing 100080, Peoples R China
; Inst High Energy Phys, Beijing 100039, Peoples R China
We study the stability of the effective Higgs potential in the split supersymmetry and Little Higgs models. In particular, we study the effects of higher dimensional operators in the effective potential on the Higgs mass predictions. We find that the size and sign of the higher dimensional operators can significantly change the Higgs mass required to maintain vacuum stability in Split SUSY models. In the Little Higgs models the effects of higher dimensional operators can be large because of a relatively lower cutoff scale. Working with a specific model we find that a contribution from the higher dimensional operator with coefficient of O(1) can destabilize the vacuum.