Diversity analysis and a genetic structure study of 25 lentil landraces (<italic>Lens culinaris</italic> Medik.) from the northern east part of the Iberian Peninsula were carried out. 8 isozymes: PGI, PRX, LAP, 6PGD, GOT, SKDH, PGM and ME, have been used for this purpose having found 17 loci for them, with 52.94% polymorphic loci and a total amount of 21 alleles. All populations show between 18 and 26 alleles. Genetic distance (D) was 0.123. Diversity parameters show similar or higher levels compared to other autogamous plant populations. They show an heterozygote defect. Coefficient of homozygotes among populations (G<sub>ST</sub>) value 0.414, was similar to Inbreeding coefficient among populations (F<sub>ST</sub>) that was 0.454. Main component analysis showed that the most important isozymes in the characterization process were GOT-3 and PGM-2. Four groups of populations were obtained by cluster analysis. This information reveals new data for improving their use in the germplasm banks for crop programs.