To understand the molecular mechanism of maize heterosis, differential gene expression patterns in the functional leaves of 35 maize hybrids relative to their parents involving 10 elite inbreds at milk filling stage were analyzed by using cDNA-AFLP. The correlation analyses of various differential expression patterns with the performance and heterosis of main maize agronomic traits were evaluated. The main results were as follows: For uniparental specific expression, significant positive correlations were detected with the performance of seed weight per ear and 100-seed weight at 0.01 and 0.05 probability levels respectively. For biparental specific expression, significant negative correlations were detected with the performance of ear diameter and seed weight per ear at 0.01 probability level. For uniparental specific expression, significant positive correlations were detected with the heterosis of ear diameter and seed weight per ear at 0.01 and 0.05 probability levels respectively. For biparental specific expression, significant negative correlation was detected with the heterosis of ear diameter at 0.05 probability level. However, for F1-specific expression, for fragments detected only in one parent and F1, and for fragments detected only in two parents or only in F1, no significant correlation was detected with the performance or heterosis of all agronomic traits surveyed.