Five inbred lines of cucumber were crossed in all possible combinations, without reciprocals, to produce ten gynoecious hybrids suitable for the greenhouses culture. All genotypes were evaluated in the greenhouses in two consecutive seasons of 2004/05 and 2005/06. Data were collected on relative increasing in plant height, length of stem internodes, number of lateral branches, number of leaves on stem, days to anthesis, early yield, total yield, average fruit weight, fruit length and fruit diameter. The amounts of herterosis for those traits were calculated. Heterosis was found to be significant for all characters measured. Generally, heterosis over mid-parents was clearly manifested in most crosses for the examined traits, while heterosis over high parent was less expressed with relatively low amounts. Conversly, negative heterosis was detected in the F₁ populations for days to anthesis, meaning that they were earlier in the first female flower anthesis than their parents. It was observed the superiority of certain F1 hybrids in relation to their parents. Meanwhile, other crosses did not exhibit significant heterosis over their parents according to their combinations. In conclusion, the choice of parents to produce hybrids and selection of the best  parents from different genetic resources is required to produce superior hybrids.