Observations of clouds over the Antarctic Peninsula during summer 2010 and 2011 are presented here. The peninsula is up to 2500 m high and acts as a barrier to weather systems approaching from the Pacific sector of the Southern Ocean. Observations of the number of ice and liquid particles as well as the ice water content and liquid water content in the clouds from both sides of the peninsula and from both years were compared. In 2011 there were significantly more water drops and ice crystals, particularly in the east, where there were approximately twice the number of drops and ice crystals in 2011. Ice crystals observations as compared to ice nuclei param-eterizations suggest that secondary ice multiplication at temperatures around −5° C is important for ice crystal formation on both sides of the peninsula below 2000 m. Also, back trajectories have shown that in 2011 the air masses over the peninsula were more likely to have passed close to the surface over the sea ice in the Weddell Sea. This suggests that the sea-ice-covered Weddell Sea can act as a source of both cloud condensation nuclei and ice-nucleating particles.