Abstract: Landfill Gas (LFG) is classified as the main source of methane, a greenhouse gas, caused by human activities. On the other hand methane is an important energy element. Also, it can cause fires in landfill. On these bases, estimation of methane generated out of landfills has been highly important to scientists, decision makers and owners of landfills. The purpose of this study is to review most used models which predicts LFG. As a result, these models can be classified in zero order, first order and second order decay, mathematical and numerical models. First order decay models, which are used more all over the world, has been considered in more details as multiphase models which result in more appropriate estimations. However, numerical models can lead to more accurate results.