Our study investigates the overall effects of in-store displays (ISD) on category sales and brand market share in an online shopping context, and compares the differences in effectiveness between ISD types. Using data from an online grocer, we examine three online ISD types that match with traditional ones: first screen (entrance), banner (end-of-aisle) and shelf tag (in-aisle) displays. Empirical results for 10 categories confirm that online ISD may substantially increase brand market share and to a lesser extent, category sales. Our results also demonstrate that not all types are equally effective. First screen displays clearly have the strongest effect on market share: they benefit from their placement on the ‘entrance’ location, central on-screen position and direct purchase link. While they only feature 1 SKU, banner displays typically feature all SKUs of a brand, yet, are placed on border-screen positions on traveling-zone pages without a direct purchase link. Based on our results, the advantage of banner displays does not weigh up against the advantages of first screen displays in most cases. Shelf tags, finally, may be very useful in attracting attention to interesting promotions, but appear to have no or at most a limited effect on their own.