Background and purpose Tumours are now considered as complex tissues including endothelial cells of the tumour vasculature, which can decrease radiotherapy efficacy. It is thus important to better characterise the response of both types of cells to irradiation. This study investigated the effects of X-ray and alpha particle irradiation on cancer and endothelial cells. Materials and methods A549 non-small-cell lung adenocarcinoma cells and human endothelial cells (EC) were exposed to X-rays or alpha particles. Responses were studied by clonogenic assays and nuclei staining. A gene expression study was performed by using Taqman low density array and the results were validated by qRT-PCR and ELISA. Results The relative biological effectiveness of alpha particles was estimated to be 5.5 and 4.6 for 10% survival of A549 cells and EC, respectively. Nuclei staining indicated that mitotic catastrophe was the main type of cell death induced by X-rays and alpha particles. Both ionising radiations induced the overexpression of genes involved in cell growth, inflammation and angiogenesis. Conclusions Alpha particle irradiations are more effective than X-rays. The gene expression changes observed in both cell types after alpha particle or X-ray exposure showed possible crosstalk between both cell types that may induce the development of radioresistance.