Construction and demolition (C&D) waste has become a serious environmental problem in many countries. The C&D industry in Istanbul currently generates about 55 million tons of waste per year. Quantifying C&D waste generation is regarded as a prerequisite for the implementation of successful waste management. This paper describes some existing C&D waste quantification methodologies. A case study in which the Fatta et al. estimating model was applied to estimate the generation of C&D waste in Istanbul is also presented and compared to the current estimation results. The study has evaluated C&D waste quantification and showed the differences of the results. It is recommended that being on the safe side the new estimation results are taken while planning the recycling and landscaping areas of the city and the country for the future. Also an inventory of all C&D waste generated in the country can be carried out in order to assess the feasibility of large scale recycling and storing of C&D waste to choose the most suitable and applicable method and to direct future studies for better quantification methods.