Purpose: The aim of the present crossover study was to evaluate professional toothbrushing as a method for diagnosing gingivitis in children. Materials and Methods: Thirty-four preschool children who had gingival bleeding >= 10% and without proximal restorations/carious lesions were included in the study. Examinations comprised two gingival indices recorded at a 15-min interval, in the following sequences: the Ainamo and Bay gingival bleeding index (GBI1) followed by the brushing index (BI2) and vice versa (BI1-GBI2). Half of the children started the study in the first sequence and the other half in the second. After a 3- to 4-day washout period, the indices were again recorded with individuals changing the sequences. Data analysis considered GBI as the gold standard, and sensitivity (SE), specificity (SP), positive predictive value (PPV) and negative predictive value (NPV) were also calculated. Results: The overall mean value of gingival bleeding at the first examination was 18.85 ± 9.24%. Validation of toothbrushing performed after GBI (BI2) resulted in values for SE, SP, PPV and NPV of 0.59 (95% CI, 0.55 to 0.63), 0.92 (95% CI, 0.91 to 0.93), 0.64 (95% CI, 0.60 to 0.69) and 0.90 (95% CI, 0.89 to 0.92), respectively. BI performed before GBI (BI1) resulted in similar SE, SP, PPV and NPV. Percentage agreement of GBI1-BI2 and BI1-GBI2 was 83.5% and 85.9%, respectively. Conclusions: Professional toothbrushing can be suggested as a method for the diagnosis of gingival inflammatory status in children, especially as an indicator of gingival health. Keywords: children, diagnosis, gingivitis, periodontal index, primary dentition