This report addresses wide-spread concerns regarding the quality of ECEC provisions and reports the results of secondary data analyses of the relations between structural quality characteristics and process quality in European ECEC provisions. The report also addresses the issue of social selection mechanisms in ECEC by reporting findings on the quality of ECEC services specifically for socioeconomically disadvantaged children and by identifying combined effects of structural and contextual factors disfavoring disadvantaged children. Using data from longitudinal datasets of ongoing studies in five European countries, comparative analyses were conducted on a comprehensive set of structural variables, measured in a similar way across these countries, to investigate their associations, with observational measures of process quality. In addition to the commonly investigated main effects, the current study also specifically explored interaction effects for different combinations of teacher, classroom and system characteristics. Finally, we investigated whether children from socioeconomically disadvantaged background involved in these studies experienced equal process quality as non-disadvantaged children. (author abstract)