The beneficial mechanical properties provided by greater diameter or short implants increased their usage in the tilted implant concept. The aim of the present study is to compare the stress distribution of four different treatment models including variable implant numbers and diameters under static loading protocol in the atrophic mandible using 3-dimensional finite element analysis. Three models included two tilted and two vertical positioned implants with different diameters, whereas distally placed two short implants were added to the fourth model. The von Mises stress, maximum and minimum principal stress values were evaluated after applying 200N bilateral oblique loads to the first molar teeth with the inclination of 450 to the longitudinal axis. Tilted implants were associated with higher stress values when compared with vertical implants in all models. The lowest stress values were obtained in the fourth model including short implants. Although all stress values showed slight increases by descending implant diameters, the stress values of the model including implants with 3.3 mm diameter were within physiologic limits. All in all, increasing number or diameter of implants may have a positive effect on implant survival. In addition, when narrow diameter implants need to be inserted in the tilted implant concept, combination with short implants may be recommended for long term success.