In this Thesis entitled "Analysis and improvements in the evaluation of several terms of medium-term beach evolution models" a medium-long term beach evolution model is developed and applied in refraction-diffraction areas. The Thesis is composed of the following main sections: SECTION 2. Fundaments and development of a medium-long term beach evolution model In this section a medium-long term beach evolution model is developed and validated based on field data. SECTION 3. Breaking wave characteristics in refraction-diffraction areas for beach evolution models In this section a method to determine the breaking wave characteristics in refraction-diffraction areas is proposed and validated. SECTION 4. Equilibrium beach profile for refraction-diffraction areas In this section an analytical expression to calculate the equilibrium beach profile for refraction-diffraction areas is derived, being calibrated based on field data.