1. Abstract The paper presents results from a dual study based on pre- and post interviews with 600 grocery shoppers who shopped both virtually and in real life in the same store. The shoppers were asked to identify products that they had just purchased on impulse in a post-shopping interview. There is a strong impulse effect in a grocery store. The shopping basket of customers that used a shopping list had the same share of impulse product that the customers without a shopping list. This is a surprising and interesting finding. Moreover, the study shows that the customers tend to label a product an impulse product when he or she had not planned to buy anything in a particular category.