Oatmeal is widely recognised for its health benefits and is often used in breakfast cereals due to its favourable nutritional profile and naturally gluten-free nature. Quick-to-prepare cereals with a variety of flavours are particularly popular among consumers. Instant oatmeal is often enriched with ingredients, such as freeze-dried raspberries, apple, chocolate, coconut, etc., that enhance taste and palatability. Nutritional labelling can reveal unexpectedly high sugar content and, in some cases, the presence of gluten. This study compared the declared nutritional values ​​of oatmeal (10 packs) with those of instant oatmeal (65 packs) available in Belgrade, Serbia, in July 2025. Sugar content was significantly higher in instant cereals (median 16 g/100 g) than in oatmeal (median 0.85 g/100 g). Protein content was higher in oatmeal (median 14 g/100 g) than in oatmeal products (median 11 g/100 g). The quantities of total fat (median 7.8 g/100 g vs. 6.85 g/100 g) and saturated fatty acids (median 2.1 g/100 g vs. 1.0 g/100 g) were slightly higher in instant cereals. Carbohydrate content was slightly lower in oatmeal (median 56 g/100 g) than in oatmeal products (median 63 g/100 g), and energy values ​​followed the same trend (median 1624 kJ/100 g versus 1534.5 kJ/100 g). Despite oats being the main ingredient in both products, the addition of different ingredients significantly affects the nutritional profile and consumer perception of instant cereals compared to plain oatmeal. These findings are relevant both for consumers, who are concerned about the sugar content of flour, and for manufacturers developing instant oatmeal formulations.