Improved non-LTE line formation calculations for hydrogen in O-stars are presented. The calculations are carried out by means of the method recently developed by Werner and Husfeld (1985) and use an extensive hydrogen model atom with 10 non-LTE levels and 55 transitions. For most of the transitions Stark-broadening is included in the statistical equilibrium. Compared with observed high quality Balmer line profiles of massive O-stars, sdO-stars and central stars of planetary nebulae, the new calculations yield significantly better agreement than previous ones. The improvements are of particular importance for the quantitative spectral analysis of central stars where they lead to systematically higher effective temperatures.