Dataset contains lake sediment accumulation data from 213 different lakes in boreal Finland that can be used to calculate modern carbon (post 1986) sediment accumulation rates. Sediments have been collected between the years 2005 and 2016 using Kajak and Limnos type sediment core samplers. Sampling depth was recorded using a hand held or hull attached depth echo sounder. After collection, sediment has been sliced to samples primarily in 1 cm intervals ( n = 180), but in some cases (n = 35) compound samples of 2-6 cm have been used and one core has been sliced with 0.5 cm interval. Sediment weight has been measured when wet and after being dried in a low temperature (95 °C) oven. Topmost two centimeters of the sediment core data have been eliminated from the data set to reduce the chance of sediment mixing and biological processes affecting carbon accumulation calculations.Sediment have been dated using the fallout of 1986 Chernobyl nuclear event derived 137Cs activity. Cs activity was measured by gamma spectrometers: An EG&G Ortec ACE™-2K (GTK, Finland) equipped with a four-inch NaI/TI detector, and a BrightSpec bMCA-USB pulse height analyzer (GTK, Finland) together with a well-type NaI(Tl) detector. Highest activity is interpreted as the 1986 age. The carbon and nitrogen concentration measurements have been measured using Elementar Vario Max CN-analyzer (Labtium, Finland). C:N ratios have been calculated as molar ratios.Included in the dataset are lake basic lake morphometric features such as lake size, elevation from sea level, shoreline length and mean depth from National Land Survey of Finland and Finnish Environment institute databases. Catchment data includes the size of the catchment and the land use coverage percentages obtained using the Finnish Environment Instutes VALUE catchment delineation tool. The extent of ditch drainage networks within individual catchments was isolated from National Land Survey of Finland data, and the area of ditch drainage was calculated using 40 meter spatial buffer from the ditches in ArcGIS Pro.Spatial coverage: Sediment sampling locations are located within the area 60,096 - 64,965 °N and 22,349 - 28,84 °E (decimal degrees, WGS84).