This investigation was carried out at Kaha Vegetable Research Farm, Kalubia Governorate, Egypt 2015 and 2016 to study heterosis percentage over mid and better parents, potence ratio and correlation coefficient between traits for some important economical characters in cucumber. Five different parental lines of cucumber obtained from Cornell University which included parental line"1380-1"(P₁); parental line"87- 674-1"(P₂); parental line"99-340"(P₃); parental line"99-357"(P₄) and parental line"99-347"(P₅) were carried out by 5 x 5 half diallel mating design, the experimental design was  randomized complete block with three replicates. The obtained results generally that the utilized parental lines appeared to have wide ranges of diversity in the different studied traits and their indicated differences were found significant in the most situations. The results exhibited that the highest significant heterosis (47.30%) was reported for early yield per feddan(ton) followed by total yield  per feddan (45.81%) and fruit shape index (40.78%), while the largest significant heterosis over better parent (33.97 and 32.86%) was recorded for early yield per feddan followed by (31.53 and 31.50% ) for total yieldThe results illustrated that plant length(cm) and number of leaves per plant exhibited significant and positive genotypic and phenotypic correlation with fruit length(cm), fruit shape index(cm), early yield per feddan(ton), average fruit weight(g), number of fruits per plant and total yield per feddan (ton). These positive correlations indicated that a selection programme based on any of these traits will be resulted in increasing yield. Negative and significant association was estimated with days to anthesis first female flower and fruit diameter(cm).