Coated papers have emerged as alternatives to petroleum-based and non-biodegradable plastics, particularly in packaging industries. Indeed, barriers brought by the coating layer, toward oxygen for example, allow better food preservation. This growing interest in the field of packaging has led to the need to characterize the mass transfer properties of these materials, particularly oxygen. Although methods and standards to characterize these parameters have been developed for plastic materials, none have been specifically adapted for coated cardboards. This paper evidences a so-called "edge effect" occurring when characterizing the oxygen transmission rate (OTR) of single-side coated cardboards. This leads to two significantly different OTR values depending on the material's side, cardboard, or polymer coating, exposed to the oxygen flux. Over-or underestimated OTR can have a significant impact on food preservation. Therefore, avoiding edge effects is essential for obtaining accurate oxygen transmission rate value. This study focuses on one measurement method and two cardboard supports. Depending on the equipment used and sample properties, different methods can be used to prevent edge effects and must be investigated on a case-by-case basis.