We examined the relationship between, and variations in, particulate organic carbon (POC) and particulate organic nitrogen (PON) based on previously acquired ocean and inland water data. Some new points were found beside the traditional latitude, depth and temperature dependence of POC, PON and POC/PON. The global average value of POC/PON (7.54±3.82) is higher than the Redfield ratio (6.63). The mean values of POC/PON in south and north hemisphere are 7.40±3.83 and 7.80±3.92, respectively. The high values of POC/PON appeared between 80° N~90° N (12.2±7.5) and 70° N~80° N (9.4±6.4), and relatively low POC/PON were found from 20 °N (6.6±2.8) to 40 °N (6.7±2.7). The latitudinal dependency of POC/PON in the northern hemisphere is much stronger than in the southern hemisphere. Variations of POC/PON in inland water also showed similar latitude-dependency of POC/PON in ocean water, but significantly regulated by lake’s morphology, trophic state and climate, etc. factors. Higher POC and PON could be expected in the coastal water, while POC/PON significantly increased from 6.89±2.38 to 7.59±4.22 in north hemisphere with the increasing rate of 0.0024/km. The coupling relationship between POC and PON in oceans is much stronger than in inland waters. Variations in POC, PON and POC/PON in inland waters should receive more attention due to the importance of these values to global carbon and nitrogen cycles and the indeterminacy of the relationship between POC and PON.