Two NS-sunflower (Helianthus annuus L.) hybrids, differently resistant to Diaporthe / Phonopsis helianthi, and their parental lines were examined on the effect of ageing and position on leaf growth parameters and photosynthetic potential of leaves. It was found that both hybrids, NS-H-26 and NS-H-43, had higher rates of leaf appearance, leaf expansion and leaf area duration than their parental lines. Heterotic effect was especially noticeable in leaf area formation, in both hybrids. Most of the examined parameters point to the similarity between the hybrid NS-lt-26 and its female pârenr and between the hybrid NS-H-43 and its male parent. The hybrid NS-H-43 followed a patrern of the male parent RFIA-SNRF in photosynthetic potential of the examined leaves too.