The purpose of this research was to understand how individuals reflect on the frequency and quantity of foods that they consume. Participants selected 5 males and 15 females aged 30 years or older were first interviewed on the frequency of their food consumption. Then based on this data, they were given a cognitive interview using the method of verbal proving. The individual cognitive interviews were recorded with consent while being conducted after complete approval by the Seoul National University Institution Review Board. The recorded material was evaluated using a thematic analysis after transcribing them into text. By analyzing stages of reflection, the major barriers to make the device difficult are revealed: 1) More difficulty in remembering events over the course of a full year due to diversification in the types of food that people consume 2) difficulty calculating the average for seasonal foods 3) difficulty estimating the amount of consumption from the photos presented 4) difficulty estimating amount of consumption from the quantity presented 5) difficulty processing foods that people think are healthy and foods are unhealthy simultaneously 6) difficulty having to consider foods where target food goes in as an ingredient; 7) difficulties arising from having to increase frequency when the amount consumed is higher than the quantity that is presented 8) difficulty having to combine the frequency and quantity of each food item when numerous foods are clustered into one category. These findings show that the less participants were involved in cooking, the more diverse their eating habits were, and the more they tried to adhere to rules of filling out the questionnaire, the more it was difficult for them to come up with an answer to the question being asked. It therefore seems necessary to construct a Food Frequency questionnaire that is attentive to these problems that arise from the recall stages.