Abstract: The distribution, sources and ecological risks from 16 polycyclic aromatic hydrocarbons (PAHs) in surface seawater in Liaodong Bay and in an offshore petroleum exploration area in the Bohai Sea, China, were investigated from May 2014 to August 2015. Statistical analysis results (e.g. cluster analysis) were used to establish the relationships between different parameters, and the risk quotient was applied to assess ecological risk. The individual PAHs with the highest concentrations were naphthalene (20.6-288.5 ng/L) and phenanthrene (19.2-59.5 ng/L). The PAHs concentrations were higher in May/June than in August, and showed a seasonal variation. The pollution caused by the 16 PAHs in the surface seawater in both Liaodong Bay and in the offshore area over the study period was classified as low to moderate. The concentrations of PAHs were generally high in the southwest of Liaodong Bay, the sea area of Jinzhou Bay, Pulandian Bay and in the Liaohe and Daliao estuaries. In Liaodong Bay, PAHs were dominated by two-and three-ring compounds. Analysis of isomer ratios indicated that the main sources of the PAHs contaminants in Liaodong Bay were petroleum sources. The PAHs posed moderate ecological risks in both Liaodong Bay and the offshore petroleum area. The contributions of individual PAHs to ecological risk varied, with high molecular weight PAHs posing greater ecological risk than low molecular weight PAHs; the contribution to ecological risk from the high molecular weight PAHs was 50%-82%. The ecological risk from benzobfluoranthene was high. The investigation provided important information about the pollution levels of 16 PAHs in surface seawater in Liaodong Bay, and highlighted the need to prevent and control pollution from PAHs in the region.