Computer simulations were performed to evaluate the inherent differences between the dual energy computed tomography methods proposed by Cann et al, Laval-Jeantet et al and Goodsitt et al, and the conventional single energy method for bone mineral estimation. The influence of fat content on the accuracy of these methods was compared. According to the results, all dual energy methods were more accurate in estimating bone mineral than did the single energy method. Different performance characteristics among dual energy techniques were also observed. By understanding these characteristics and applying them correspondingly, maximum accuracy in mineral estimation may be obtained.