In this study, inventory models are considered in which inventory is depleted not only by demand but also be deterioration. A probabilistic order level model with stochastic demand for exponentially deteriorating items is developed in the case of back-orders and lost-sales. An order level model with deterministic and constant demand is developed for exponentially deteriorating items in which the demand pattern follows power pattern. A probabilistic schedulling period model with stochastic demand is developed for nondeteriorating and exponentially deteriorating items in which the demand pattern follows power pattern. A case problem for each model is solved either by exact formula or numerical solution procedure to show the effect of the parameter on the optimal solutions.