Concentrations of particulate and dissolved organic carbon from water samples collected throughout the ice-free season in the Lena River Delta, supplemented with samples from Central Siberian Rivers Kochechum and Nizhnyaya Tunguska. Particulate samples were obtained by filtering water through pre-combusted glass-fibre filters, dissolved organic matter was studied in the filtrate. Molar concentration ratios of organic carbon to nitrogen in particulate samples are additionally reported as well as stable carbon isotopic composition (δ13C in ‰ VPDB) and radiocarbon content (∆14C in ‰) of particulate and dissolved organic carbon.