Objective: To examine ethnic differences in lung function in relation to anthropometry, social and psychosocial factors in early adolescence. Methods: 3924 pupils aged 11-13yrs, 80% were ethnic minorities, with satisfactory lung function measures. Data were collected on economic disadvantage (SES), psychological well-being, tobacco exposure, height, Forced Expiratory Volume (FEV₁) and Forced Vital Capacity (FVC). Results: The lowest FEV₁ was observed for Black Caribbeans/Africans after adjusting for standing height (SH) (Whites: boys 2.475Litres [95% Confidence Interval 2.442, 2.509], girls 2.449L [95%CI 2.464, 2.535]; Black Caribbeans: boys -14% [-16, -12], girls -13% [-16, -11]; Black Africans: boys -15% [-17, -13], girls -17% [-19, -14]; Indians: boys -13% [-16, -11], girls -11% [-14, -8]; Pakistanis/Bangladeshis: boys -7% [-9, -5], girls -9% [-11, -6]). Adjustment for upper body segment (UBS) instead of SH achieved a further reduction in ethnic differences of 41-51% for Black African origin children, and 26-39% for the other groups. Overcrowding (boys) and poor psychological well-being (boys and girls) were independent correlates of FEV₁, explaining up to a further 10% of ethnic differences. Similar patterns were observed for FVC. Social exposures were also related to height components. Conclusions: Differences in UBS explained more of the ethnic differences in lung function than SH, particularly among Black Caribbeans/Africans. Social correlates had a smaller but significant impact. Future research needs to consider how differential development of lung capacity is compromised by the social patterning of growth trajectories.