In this work, we show existence and uniqueness of positive solutions of H(Du, D 2 u)+ χ(t)|Du| Γ − f (u)ut = 0 in Ω × (0, T ) and u = h on its parabolic boundary. The operator H satisfies certain homogeneity conditions, Γ > 0 and depends on the degree of homogeneityof H, f > 0, increasing and meets a concavity condition. We also consider the case f ≡ 1 and prove existence of solutions without sign restrictions.