The C:N ratio in settling particulate organic matter (POM) in the sea is primarily determined by the composition of newly produced organic matter in the overlying surface water and its subsequent differential decay along the water column. It is therefore directly connected to both the availability of dissolved nitrogen for primary production and the efficiency of the carbon pump. Little is known about the way lateral transport of organic and lithogenic particles from the continental rivers/shelf/slope affects the C:N ratio of the settling POM at the deep-sea. In this study we measured particulate organic carbon (POC) and nitrogen (PN) and their ratios in time-series sediment traps (DeepLev observatory, 50 kms offshore) and in suspended particle profiles in water column at the ultra-oligotrophic southeastern Mediterranean Sea. Measurements were conducted in both high (in winter) and low suspended particle transport periods (HTP and LTP, respectively). Significantly higher POC:PN molar ratios were measured near the surface during HTP compared to LTP (7.2 and 5.8, respectively). Using reported POC:PN ratios in suspended sediments over the shelf we calculated that the higher POC:PN ratios in the open sea sediment traps during HTP resulted from mean contribution of approximately 40% of shelf-derived POM arriving via lateral transport. Moreover, increase with depth of the POC:PN ratio was significantly milder during HTP compared to LTP. This change is attributed to the refractory nature of the laterally transported POM and its association with ample lithogenic particles, which may increase settling times and scavenge dissolved organic matter onto particle surfaces.