Abstract. Aerosol light scattering, backscattering and absorption were measured at Montsec (MSC; 42°3' N, 0°44' E, 1570 m a.s.l.), a remote high-altitude site in the Western Mediterranean Basin. Mean (± sd) scattering, hemispheric backscattering and absorption were 18.9 ± 20.8 Mm−1, 2.6 ± 2.8 Mm−1 and 1.5 ± 1.4 Mm−1, respectively at 635 nm during the period under study (June 2011–June 2013). Mean values of single scattering albedo (635 nm), scattering Ångström exponent (450–635 nm), backscatter-to-scatter ratio (635 nm), asymmetry parameter (635 nm) and black carbon mass absorption cross section (637 nm) were 0.92 ± 0.03, 1.56 ± 0.88, 0.16 ± 0.09, 0.53 ± 0.16 and 10.9 ± 3.5 m2 g−1 respectively. The scattering measurements performed at MSC locate this site in the medium/upper range of values reported for other mountaintop sites in Europe mainly due to the frequent African dust episodes and regional recirculation scenarios occurring mostly in spring/summer and causing the presence of polluted layers at the MSC altitude. Under these conditions no clear diurnal cycles were observed for the measured extensive aerosol optical properties (scattering, absorption and extinction). Conversely, the mean particle absorption at MSC was relatively lower compared with other EU remote stations thus leading to relatively higher single scattering albedo compared with most European data. A season-dependent decrease in the magnitude of aerosol extensive properties was observed when MSC was in the free troposphere with the highest free-troposphere vs. all-data difference observed in winter and the lowest in spring/summer. The slope of the scattering vs. absorption relationship (among the lowest reported for other mountain top sites worldwide) indicates that the MSC site is dominated by dust aerosols at high aerosol loading. Correspondingly, scattering Ångström exponent and asymmetry parameter respectively decreased and increased indicating the shift toward larger particles associated with African dust episodes. The black carbon mass absorption cross section showed a clear annual cycle with higher values in summer when the occurrence of African dust outbreaks and regional recirculation scenarios favour the presence of aged black carbon particles in polluted layers at the MSC altitudes. The optical measurements performed at the MSC remote site were compared with those simultaneously performed at a regional background station in the Western Mediterranean Basin.