Electromagnetic absorbing materials can be classified into: conventional absorbers, metamaterial absorbers, and reconfigurable absorbers. This paper includes a short survey on these types and there applications. It also includes the design of a thin electromagnetic absorber. The absorber is based on mushroom-like electromagnetic band gap structure with square patches. A simple procedure is developed to design the absorber. The design is checked by simulation using HFSS package. The effect of changing dimensions of the structure on absorption is evaluated. The results of the parametric study were used to trim the design and get more accurate dimensions of the structure.