This paper addresses the sustainable development of the Flemish greenhouse industry by investigating the optimal size, structure and location of its farms. It emphasizes the importance of a square shape of the greenhouse as optimal structure. Using Data Envelopment Analysis an optimal farm size that varies between 1.7 and 3 hectares has been found, depending on the method used. Location factors that matter in the future Flemish greenhouse industry include temperature, light, transportation costs, air pollution and land prices, while rainfall, wind, output price differences, soil and infection risk do not differentiate between regions.