Quantitative information on parents' preferences regarding multiple vaccine injections and on work-loss due to vaccination is important to guide decision making on the use of combination vaccines for universal vaccination. Our survey in families of 1347 toddlers (18 -- 24 months) and 1315 adolescents residing in Flanders, Belgium, revealed common attitudes in both age groups. The majority of parents would allow maximum two injections in one visit. 39% were not willing to pay anything to avoid a concomitant injection, whereas the remainder mentioned amounts around a median of c.20. The responses were hardly influenced by the socioeconomic determinants studied and the concordance between the number of concomitant injections parents would allow and their willingness-to-pay assessed by an open-ended question was limited, which suggests that more sensitive quantification using other methods would be useful. Work-loss due to vaccination was assessed for infants only and was rare (4.5%).