In this paper, the Data Envelopment Analysis (DEA) is proposed for benchmarking Life Cycle Impact Assessment (LCIA) results of a sample of Wastewater Treatment Plants (WWTP) is presented. DEA inputs are the normalized values of seven impact categories. A constant unit output is the functional unit of the LCIA analysis. Several DEA models have been applied. The results of the different DEA models were very consistent, with three of the WWTP labelled as efficient and one of them especially super-efficient. The proposed approach allows the identification and ranking of the inefficient units.