The aim of the present study was to examine whether immaturity of cardiorespiratory control corresponds to a less mature behavioural state pattern and/or to less efficient feeding behaviour. Fifty-four infants were observed and data polygraphically recorded for 6 hours; a feeding session was included. It was found that infants with immature cardiorespiratory control spent more time in REM-sleep, less time in the active awake state, and were more likely to be inefficient feeders. In addition, 100 infants were observed for risk signs of sudden infant death syndrome and their parents were asked to answer a questionnaire on the sleeping and feeding behaviour of their infants. The majority of the infants with immature cardiorespiratory control were described as bad feeders but good sleepers. We conclude that gathering information about sleeping and feeding behaviour is useful when screening for immaturity of cardiorespiratory control.