The omnipresence of plastic litter in the marine aquatic environments is a major environmental problem, and micron sized plastic particles have been detected in many species of fish and shellfish consumed by humans. The present study aimed at characterizing the occurrence, the shapes, dimensional classes, counts and polymer type of plastic ingestion by N. norvegicus individuals (n = 20) collected from two wild populations of the Adriatic Sea (Fig. 1), focusing on three different anatomical compartments (gut, hepatopancreas and tail), separately analysed. The outcomes of the present study point out that MPs were found in all the investigated individuals with an average of about 17 MPs/individual. Particles were predominant over fibers with a ratio of about 3:1. The majority of both the particles and fibers were in the dimensional range of 50 - 100 µm while the majority of the fibers were in the dimensional range of 50 µm- 300 µm (Table 1). The predominant polymers were Polyester, Polyamide 6, Polyvinyl Chloride and Polyethylene which were found in all the investigated individuals and that, together, constitute about 61% of all the MPs found. Among the three investigated compartments, particles concentrated more in the hepatopancreas than gut and tail, with no significant difference between the latter. While, fibres concentrated more in gut and hepatopancreas than in tail, with no significant difference between the first two. The dimensional class of the MPs significantly affected their anatomical distribution, finding only the smaller ones in the tail (p ¡ 0.05). Overall, no statistical differences between individuals from the two sampling sites (off Ancona and Pomo Pits) were observed. Neither sex, length nor weight of the individual influenced the level of retained MPs.