In this work, we have investigated the effect of changes in the properties of planar surfaces on the attachment and viability of two bacterial species of medical relevance. Polydimethylsiloxane (PDMS) surfaces showed a promising repellent effect on both live and dead E. coli and S. aureus cells. When the hydrophilicity of the PDMS was increased by UV-radiation this repellent effect disappeared. On gold surfaces coated with hydrophobic and hydrophilic self assembled monolayers (SAM) very few bacterial cells were found, compared to plain gold. Moreover, the behaviour of E. coli and S. aureus was modulated differently by the surface properties. Thus, while S. aureus cells lived in slimy conglomerates and colonised the surfaces at the same high density from both diluted and concentrated solutions, in contrast, single cells of E. coli colonised the surfaces at lower densities from diluted solutions. Also, dead E. coli cells were easily washed off from most surfaces, whilst dead S. aureus cells were frequently found attached to the surfaces, which may also be explained by its occurrence in conglomerates. Strain specific bacterial physiology and reactivity to these surfaces may possibly also be a factor in influencing the interaction. These initial results contribute to the purposeful design of species-specific pro-or anti-bacterial surfaces for the use of lab-on-a-chip devices and medical devices.