The Papaver dubium group (Papaveraceae) in Belgian Lorraine. – During a research in the extreme south of Belgium, the plants of P. dubium s.l. could be divided into three ‘phenotypes’ (P1, P2 and P3) based on a combination of characters: the color of fresh and dry latex, the shape and pilosity of the buds, the shape of the capsules and secondarily some characters of the rosette leaves and of the upper stem leaves. An initial distribution map was established in 2019-2020 for each phenotype. Roadsides, railway environments, cemeteries and reworked areas are the habitats most frequently occupied by these therophytes characteristic of disturbed places. Two phenotypes cohabit in numerous localities, less often the three phenotypes. P1, the most common in the region, belongs to the subspecific taxon P. dubium subsp. dubium. The rarest phenotype P2 could be related to P. dubium subsp. lecoqii and P3 to the confine taxon present notably in Germany but whose taxonomic validity is still in doubt. Two phenotypes cohabit in many localities, much less often all three phenotypes. The main objective of this article is to draw the attention of botanists and naturalists to Papaver dubium s.l. whose taxonomy and systematics are still widely controversial.