We propose a new method for approximating the optimal order-up-to level in inventory systems with compound Poisson demand process and stochastic lead-time. The approximations are derived for cost oriented inventory systems where unfilled demands are backordered. The condition under which the system behaves like a Make-To-Order system is also discussed. By means of a numerical investigation, we show that our method provides "good" approximations of the optimal order-up-to level. Furthermore, a numerical comparison of these approximations with an approximation provided in the literature for fast moving items is also conducted. Our works allows insights to be gained on the stock control of fast and slow moving items related issues.