One of the projects under the biodiversity conservation theme of the St. Lawrence Action Plan is the development of an integrated plan for conserving the St. Lawrence’s natural environments and biodiversity. Identifying the sites where the conservation needs are the most urgent was the first step in this integrated planning process leading to the production of the Atlas of sites of interest for conservation in the Estuary and Gulf of St. Lawrence coastal regions. Conservation targets (coarse filter) selected for this atlas are forested areas, inland wetlands, coastal marshes and sandy environments. For each selected targets, sites of interest for conservation were determined up to a representativeness threshold of 20% for a given spatial reference unit (e.g., territorial zones - grouping of ecological districts). To do so, sites with high conservation interest were first selected, those sites being located within or adjacent to protected areas or exceptional forested ecosystems, sites hosting species at risk, sites bordering salmon rivers, or those having unique ecological features. A prioritization analysis was then carried out on conservation targets using a multi-criteria analysis when the 20% representativeness threshold was not reached following the selection analysis. Other sites of interest not covered with the coarse filter targets and representing local sites with high conservation value were also determined (fine filter), such as bird colonies, eelgrass beds, important wildlife elements (critical habitats of species at risk, Bank Swallow and Chimney Swift nesting sites, Harlequin Duck winter concentration sites, breeding and rearing habitat for Rainbow Smelt in the southern St. Lawrence Estuary, etc.), important plant occurrences and salmon rivers.