The concentrations of eighteen perfluorinated compounds (PFCs: C5-C14 carboxylates, C4, C6-C8 and C10 sulfonates and 3 sulfonamides) were determined in wastewater and sludge samples originating from two different wastewater treatment plants (WWTPs). The analytes were extracted by solid phase extraction (dissolved phase) or sonication followed by solid phase extraction (solid phase). Qualitative and quantitative analyses were performed by LC-MS/MS. According to the results, perfluoropentanoic acid (PFPeA), perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) were dominant in wastewater and sludge samples from both plants. The average concentrations in the raw and treated wastewater ranged up to 75.7 ng L-1 (perfluorotridecanoic acid, PFTrDA) and 76.0 ng L-1 (PFPeA), respectively. Concentrations of most PFCs were higher in effluents than in influents, indicating their formation during wastewater treatment processes. In sewage sludge, the average concentrations ranged up to 6.7 ng g(-1) dry weight (PFOS). No significant seasonal variations in PFCs concentrations were observed, while higher concentrations of PFOA, PFOS and perfluorononanoic acid (PFNA) were determined in the WWTP receiving municipal and industrial wastewater. Significantly different distribution coefficient (K-d) values were determined for different PFCs and different type of sludge, ranging between 169 L kg(-1) (PFHxS) to 12,922 L kg(-1) (PFDA). (C) 2012 Elsevier B.V. All rights reserved.