In this study we compare the influence of user-defined femtosecond laser generated micro structures (grooves with different widths) and self-organized superimposed nano- and micro-spike structures in titanium on the adhesion of eukaryotic cells (fibroblasts or osteoblasts) or bacteria (Streptococcus mutans, Streptococcus salivarius, Staphylococcus aureus or Pseudomonas aeruginosa). We found that the amount of adhered cells can be affected by surface structuring and subsequent changes in cell-surface contact ratio. Thus, regarding a favoured reduction in cellular adhesion, the effective structural feature size should be smaller than or equal to the cell size. In case of eukaryotic cells this can be easily realized by femtosecond laser structuring but is challenging for bacteria.