The effects of in situ annealing on positioned InAs quantum dots grown on pre-structured GaAs substrates were investigated. Atomic force microscopy and scanning electron microscopy data were used to analyze the evolution of quantum dots during post growth annealing. Two different annealing regimes are found which allow for increasing or decreasing the quantum dot size. The shape of the initially elongated QDs becomes more symmetric during annealing. Furthermore, the number of quantum dots per site can be controlled by annealing time. Additionally, it is found that the width of the occupation probability distribution decreases during annealing. The results are discussed and compared to annealing experiments with self-assembled quantum dots. (C) 2013 Elsevier B.V. All rights reserved.