Extensive research into the impact of nutrition labelling across Europe has shown that many consumers can effectively use a nutrition label to rank a food for healthiness. The present paper considers observational and laboratory evidence which has examined the impact of nutrition labelling (on food packaging and at point of purchase) on dietary behaviour. In addition, the potential counterproductive effects of foods bearing ‘healthy’ nutrition labels are examined. The observational evidence provides a useful insight into the key characteristics of nutrition label use. Those most likely to engage with nutrition labels are more likely to have a diet related disease and/or be on a weight loss diet and have a good overall diet quality. Experimental evidence, while limited, suggests that serving size information may be overlooked by consumers. In fact, there may be a tendency among consumers to overeat foods that are perceived to be healthier. The findings from the present paper suggest that if nutrition labelling is to be considered a strategy to facilitate consumers in managing their energy intake, it must coincide with salient, consistent and simple serving size information on the front of food packages and at the point of purchase. There is a clear need for more experimental research using robust methodologies, to examine the impact of nutrition information on dietary intake. In the meantime, there should be greater attention given to portion size within national dietary guidance.