The peace treaty of Colombia contemplates a crop substitution policy seeking to replace coca crops with legal alternatives. Although crop substitution diverts funding of illegal activities and provides an income to farmers, it is important to understand how the change to a variety of legal crops (coffee, sugarcane, and cacao) affects the income of farmers, and whether there is an environmental advantage of a crop over another. This study applies life cycle assessment (LCA) coupled with socioeconomic indicators to two regions, Putumayo and Catatumbo, over different policy scenarios. LCA results show that a policy success does not ensure a lower environmental impact across the board. Legal crops consume less fuel than coca crops, which reduce fuel-related impacts, but the use of fertilizer in coffee and pesticide use in sugarcane increase toxicity-related impacts. The results, however, are affected by a lack of characterization factors of agrochemicals, but once these are replaced by proxies, coca crops appear to have greater toxicity impacts. In terms of individual crops, cacao crops have a lower environmental impact than coffee and sugarcane, but it also takes the longest to harvest, which may pose a financial risk to farmers. The socioeconomic analysis reveals that for Catatumbo farmers, a policy success reduces the income, whereas for Putumayo farmers, a policy success increases income and job generation. In general, it was observed that the dynamics of the illegal supply chain vary for each region, influencing the environmental and socioeconomic outcome of the substitution policy.@en