In the last decade, reducing urban pollution and improving quality of public spaces became a more and more important issue for public administration authorities in Romania. The paper describes the development of a web-GIS solution dedicated to monitoring of the green infrastructure in Bucharest, Romania. Thus, the system allows the urban residents (citizens) to collect themselves and directly report relevant information regarding the current status of the green infrastructure of the city. Consequently, the citizens become an active component of the decision-support process within the public administration. Besides the usual technical characteristics of such geo-information processing systems, due to the complex legal and organizational problems that arise in collecting information directly from the citizens, additional analysis was required concerning, for example, local government involvement, environmental protection agencies regulations or public entities requirements. Designing and implementing the whole information exchange process, based on the active interaction between the citizens and public administration bodies, required the use of the “citizen-sensor” concept deployed with GIS tools. The information collected and reported from the field is related to a lot of factors, which are not always limited to the city level, providing the possibility to consider the green infrastructure as a whole. The “citizen-request” web-GIS for green infrastructure monitoring solution is characterized by a very diverse urban information, due to the fact that the green infrastructure itself is conditioned by a lot of urban elements, such as urban infrastructures, urban infrastructure works and construction density.