Anatomical differences were analyzed between the inbred line HA-89 of Helianthus onnuus, which is susceptible to the fungal pathogen Phornopsis/ Diaporthe helianthi Munt. Cvet. et al., and a resistant wild population of H. argophyllus. The anatomical structure of the interspecific hybrid was also studied and compared against the progenitors. Plant materials, especially leaves, were collected in the field in the period 1991-1993 at the anthesis stage of the plants. The results obtained after the analysis of the epidermal and vascular tissues were further processed using SYSTAT statistical package. The results showed that the characteristics of the interspecific hybrid were closer to the susceptible than the resistant parent component. Considering the initial assumption that differences in the dimension of the epidermal and vascular tissues could have significant influence on variability in resistance among genotypes, a negative conclusion can be drawn.