Extending prior monographies in CSR reporting (Guthrie & Parker, 1989; Deegan, Rankin & Tobin, 2002; Cho, 2009; Laine, 2009), this paper attempts to show that the quest for legitimacy is not the only one factor to explain CSR disclosure strategies in a long period. More specifically, we explore the comparative relevance of three theories, namely the regulation, media-agenda-setting and legitimacy theories. An empirical study of four French Agro-firms is carried out. The French context gives a relevant and original setting because of the issuance of two laws during the 12 last years (2001 NRE Law, decree 2002; 2010 Grenelle 2 Law, decree 2012). Firstly, we observe the effect of these regulations in CSR disclosures. Secondly, we examine whether a relationship exists between the print media coverage related to general or specific CSR concerns of food firms and their reporting practices (media-agenda-setting theory). Finally, we examine if CSR disclosure is released in response to unfavorable media attention related to each firm (legitimacy theory). In that way, we analyze the annual reports of 4 food companies, as well as press articles related to 6 major economic newspapers, over a decade (2001-2010). A grid is developed to measure the extent of disclosure of the 73 index items related to the NRE Law requirements and the food firms specific CSR concerns (Maloni & Brown, 2006). Results indicate that the legal requirements, the print media coverage according the food industry and the individual media pressure represent three explanatory and additional factors, not adversary, of CSR reporting strategy. Overall, it appears that each theory is relevant for a determined period and depends on the characteristics of the company.