The present analysis formed part of the population study of Estonian school-children and was undertaken in order to examine the relationships between lung function variables, standing and sitting height. We measured forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), peak expiratory flow and forced expiratory flows when 50 and 75% of FVC had been exhaled, and anthropometric indices in 645 healthy schoolchildren, aged 6-18 years. The growth spurt in standing and sitting height occurred between the ages of 11 and 13 years in girls, and 13 and 15 years in boys. Growth spurts of lung parameters occurred during the same periods. FVC and FEV1 showed close correlations (r = 0.89-0.94) with all anthropometric parameters and age, whereas correlation coefficients for the flows were less close (r = 0.65-0.88). In boys, correlations between sitting height and lung function variables were greater than those with standing height. Using stepwise regression analysis, in boys sitting height was selected in all lung function parameters, and in girls sitting height was never selected. We conclude that there is a very close correlation between sitting height and lung function variables. The use of sitting height in parallel with standing height in predicted values for Estonian schoolchildren would make the values more exact.