Abstract. The scope of this thesis was the development of new features for the DIANA application. DIANA is an advanced web application for the management of biological data, developed in cooperation with the Biomedical Sciences Research Center "Alexander Fleming", in the course of a previous thesis. The application offers services for the search and presentation of data relating to microRNA targets in genes. MicroRNAs are biomolecules, which have targets on genes. In case a microRNA has a target on a specific gene, it can prevent the production of the corresponding protein. In this sense, knowledge of these targets is an important tool towards the treatment of serious diseases. The data managed by DIANA are predictions of miRNA targets on genes, provided by a computational model developed by the Biomedical Sciences Research Center "Alexander Fleming". The present thesis is focused on enriching the application with additional advanced features, like an easy to use environment for the administrators of the system, a simplified search interface, an improved mechanism for providing suggestions on erroneous search terms and uploading and comparative display of predictions from methods developed by different teams. The development of the application was based on modern Software Engineering principles, such as the Model-View-Controller architectural pattern, requirements analysis based on use cases, and system testing with execution scenarios.