In this article, we propose to investigate the extension of the E2DT (squared Euclidean Distance Transformation) on irregular isothetic grids. We give two algorithms to handle different structurations of grids. We first describe a simple approach based on the complete Voronoi diagram of the background irregular cells. Naturally, this is a fast approach on sparse and chaotic grids. Then, we extend the separable algorithm defined on square regular grids proposed in [saito94], more convenient for dense grids. Those two methodologies permit to process efficiently E2DT on every irregular isothetic grids.