Among various kinds of science and technology indicators, the market size is of a special importance for decision-makers and managers since it depicts the situation of a technology in its development process in a precise and concrete way. In other words, the close relationship between this indicator and revenue and profit makes it an appropriate tool for researchers and investigators to analyze the process of the development of a technology and related companies and business. However, acquiring reliable information about market size is considered as a complicated task. Unlike indicators such as publications and citations, one cannot find required data by monitoring world wide data banks and there is no widely accepted source for such information. There are several methods for estimating market sizes. Field studies are key tools in this area. In such studies, researchers gather required information by contacting active supplying, marketing and distributing professionals directly and analyze their discrete and sometimes, contradictory data to attain an overall picture of the size and state of a certain market. Identifying costumers, segmenting them and estimating their needs to the target products are other complementary ways for forecasting market size in the forthcoming years. Nowadays, several institutions and companies design and implement market studies and disseminate market reports periodically. Such reports are considered as helpful tools for acquiring a more precise perspective to the current and future markets of different technologies. In this review, several market reports will be examined briefly. A number of reviewed reports study the overall nanotechnology market while some others are devoted to a specific field of this generic technology. The goal of the review is to reach an overall view about the global market of nanotechnology in the years to come.