We evaluate retrieval of particle backscattering at 555 nm (bbp(555)) in the Mediterranean Sea with the quasi-analytical algorithm (QAA), using newin-situconcurrent data of remote-sensing reflectance (Rrs) and inherent optical properties (IOP). WhenRrsis corrected for Raman scattering, retrievedbbp(555) are reduced between ~7% in open waters and ~3% in coastal waters. After Raman effect is accounted for, partitioned statistics within the data set for cruise and water type are rather homogeneous. QAA-retrievedbbp(555) slightly underestimates ourin-situbbp(555), thus contradicting the few previous studies, in which high overestimation was either reported or suggested. Retrieval errors are mostly caused by theRrs-IOP model. The ‘new’Rrs-IOP model that separates the influences of water and particle phase functions produces mean bias ~–3% for open waters and ~–7% for coastal waters. In contrast, the ‘old’ model, ambiguous with respect to the phase function, produces a bias ~–5% for open waters and ~–9% for coastal waters. It is also shown that regional calibration can virtually suppress bias. In all cases, RMS error remains ~19% and accounts for all errors involved. [ABSTRACT FROM PUBLISHER]