Abstract
We study some tree level processes, such as e+e− → e+e−, e−e− → e−e− and e+e− → γγ in the noncommutative electroweak model. We find that the process of e+e− → γγ does not automatically satisfy the Ward identity. To solve this problem, we assume θ0i = ~E 2 NC = 0, θµνθµν > 0 and the vanishing first order θ terms. The constrains of θ0i= ~E 2 NC = 0 and θµνθµν > 0 are used to solve the causality and unitary problems, although such theories are free of ultraviolet divergence but they still violate unitarity.