Abstract In an attempt to find generic features of the fractal growth of Au films deposited on Ru (001), a simple simulation model based on irreversible diffusion-limited aggregation (DLA) is discussed. Highly irregular two-dimensional dendritic islands of Au particles that gradually grow on a larger host lattice of Ru particles and have fractal dimension d f≈1.70 each, are generated via a multiple ad-hoc version of the DLA algorithm for single aggregates. Annealing effects on the island morphology are reproduced assuming different sticking probabilities at nearest-neighbour lattice sites of Au films on Ru(001). Using simulation data, growth of islands is described in analogy to diffusion-limited, precipitate growth with a soft impingement of precipities. This leads one to analyse thin film island growth kinetics in such fractal systems and to predict a main peak in the scattering intensity patterns due to inter-island interference.