A method for collecting products listed in an order in a product collecting system having a plurality of modules, the method including: assigning the order to a module, allocating a product listed in the order to the order if the product is already available in the module, allocating a product to the order from another module if the product of the “slow-moving” type is not already available in the module whereas it is available in the other module, allocating a product to the order from a pallet warehouse if the product of the “slow-moving” type is not already available in the module nor in another module, and releasing the order and loading the products onto a collecting carrier when all the products listed in the order have been collected in the module.