Objectives: The object of this clinical study was to compare three different aligner systems. The aim was to help the orthodontist with choosing an adequate aligner philosophy/therapy system. Materials and methods: This study included 60 randomly chosen patients. Mild to moderate cases were selected, and patients were assigned to three groups of 20 patients each. One group was treated with Invisalign (20 patients), the second group was treated with CA Clear Aligner and the third group of patients was treated with the Orthocaps aligner system. In all cases, attachments were used to additionally enhance the fitting and efficiency of the aligner. Results: All investigated aligner systems achieved the predicted goal of the treatment, although with significant differences concerning accuracy, the predicted duration of treatment and the number of refinements. Significant differences were determined, especially regarding the efficiency, duration and cost of treatments. Conclusion: Aligner orthodontics allow for handling difficult treatment cases despite different aligner philosophies, different materials and different durations of treatment. There were significant differences concerning the envisaged time of treatment. In moderate cases, a significant difference concerning duration and costs was determined. Schlagwörter: aligner, CA Clear Aligner, Invisalign, Orthocaps