This paper compares Environmental Impact Assessment (EIA) practices and effectiveness in the Portuguese islands of the Azores and Madeira. This was accomplished by qualitative appraisal and evaluation of the contents of EIA statements and the characterisation of the EIA practices. Data was collected from the islands' regional environmental agencies and from the Environmental Portuguese Agency internet database. The findings reveal that most EIA project practitioners and consultants in the islands are associated with the regional government agencies. Proposals were generally approved with 'conditions' and the diversity of project types were lower in the islands than in the mainland. There was limited follow-up on the EIA process so that evaluation of conditions compliance was scanty. Key areas identified for consideration in the development of good impact assessment practice in the islands included, the Islands' unique geographical and ecological characteristics, scale effects, intra-insular regional dimension, impact significance evaluation approaches, and training, education and development skills in EIA processes.