In brachytherapy software defines the experimental configuration of radioactive seeds appropriate to achieve the desired dose distribution in the patient. We will show you how nowadays it is possible to develop a software for brachytherapy which achieves the goal of high accuracy and speed thanks to the combination of various software toolkits: Geant4 simulation toolkit, AIDA analysis toolkit, GRID and the web. Geant4-based brachytherapy application calculates dose distribution in tissues with great accuracy, in a realistic experimental set-up derived from CT data. The AIDA analysis toolkit provides the elaboration of simulation results. It is possible to run Geant4-based brachytherapy application through a web portal, sharing distributed computing resources thanks to the integration in the GRID, making possible even to modest size hospitals to profit of advanced treatment planning tools.