This study illustrates the feasibility of using Zelterman’s, 1988 truncated Poisson estimator for determining populations and risk estimates for a variety of offenders involved in the marijuana cultivation industry. A first set of findings suggests that the size of the industry, as measured by the number of growers is substantial. Estimates indicate that about 45,000 growers were at risk of being arrested in 2002 in Quebec. Method-specific estimates indicate that there are more growers working in indoor settings than outdoor settings. One of the main findings of the study is that most hydroponics (the growing of plants in liquid) growers may receive very important financial incentives from their activities while systematically avoiding police detection. The success of hydroponics as a criminal innovation might induce other growers or would-be growers to adopt this particular technique. The organizational structure of the marijuana trade has undergone a series of transformations since the end of the 1970s. Law enforcement pressure is seen as having contributed to the development of second wave of adaptations, from outdoor (soil-based) to indoor (soil-based) marijuana cultivation. Capture-recapture methods have been shown to provide valid measures for various hidden populations. These methods build on the relative importance of a recurring pattern in an observed population. This paper explores the validity of one capture-recapture model, Zelterman’s truncated Poisson estimator, used to estimate the size of the marijuana cultivation industry in Quebec, Canada. The capture-recapture analysis draws on arrest data to estimate the number of marijuana growers “at risk of being arrested” for a period of 5 years (1998-2002). Estimates are provided for growers involved in two different techniques: (1) soil-based growing and (2) hydroponics. Tables, references