Presentation of a comparative study of four ideal weight tables applied to the same population, in order to evaluate the differences or similarities between the same. Significant differences (p<0.001) were found between the four tables studied (WHO, USA, Barcelona, Tenerife) when classifying a patient into one of the three groups defined (malnutrition, normal and obese). The maximum differences found were between the Barcelona and Tenerife tables, which classified 13,7% and 24.05% respectively as cases of malnutrition and 35.9% and 16.89% respectively as obese.