The aim of this prospective study was to compare the outcome of orthodontic therapy using two different therapeutic strategies: the labial straightwire (SW) technique and the lingual two-dimensional (2D) technique on the lower dental arch. The sample included 50 subjects (39 females and 11 males) with a complete dentition and an Angle Class I malocclusion with crowding who were treated non-extraction. The subjects were divided into two groups: group A, consisted of 25 patients (19 females and 6 males), who were treated with the lingual 2D technique, and group B, 25 patients (20 females and 5 males) treated using the labial SW appliance (Roth system). Changes in the position of the lower incisors to the A-Po and mandibular lines were measured on cephalograms and those in the transverse and sagittal planes on individual sectors of the dental arch from 2D images of model casts obtained before and after the active phase of orthodontic treatment. Standard statistical methods were used for evaluation. Both methods (when used with appropriate indications) showed comparable results. The lingual 2D technique also represents an aesthetically favourable solution for adult patients.