A content item recommendation system comprises a recommender (203) which generates a set of recommendations for content items available through a first content item distribution system. A coordination processor (205) determines an availability characteristic for a set of content items available through a second content item distribution system of a set of content item distribution systems. The availability characteristic may indicate which content items are available to a user via the second content item distribution system. The modification processor (207) then modifies a recommendation characteristic for the set of recommendations in response to the availability characteristic for the set of content items. The approach may enable or facilitate coordination between different content item distribution systems while still allowing separate and independent operation of the content item distribution systems.