Mapping green roofs in cities provides data, that can be transferred into information about benefits and disadvantages green roofs deliver. How do they improve water retention in hectolitres? How does it affect on local water management? How do green roofs affect on reducing energy demand? Air pollution? What are other benefits specific to given region? What is the potential to build green roofs? These and other questions will be taken into consideration in article from Polish Green Roof Association soon, in May.