During the 2009 Conference of the Parties meeting in Copenhagen, the Brazilian government announced voluntary targets to reduce GHG emissions, with the targets being reconfirmed in Cancun (2010) and in Durban (2011). An estimate is presented of the economic impact of alternative policies to achieve such targets, including actions to cut emissions from deforestation and agricultural production. A dynamic-recursive general equilibrium model of the world economy is used. The main results show that deforestation emissions in Brazil can be reduced at very low costs, but the cost of cutting emissions from agriculture and energy use may lead to a 2.3% drop in gross domestic product by 2020 if sector-specific carbon taxes are applied. Such costs may be reduced to 1.5% under a carbon trading scheme. The negative impact of carbon taxes on agricultural production indirectly reduces deforestation rates; therefore, directly cutting emissions from deforestation is the most cost-effective option since it does not adversely affect agricultural production, which continues to expand into low-yield, underutilized pastures and secondary forest areas.