Purpose: Inadequate gingival thickness (GT) may lead to gingival recession. Thus, early identification of patients/teeth at risk would be advantageous. In adults, the probe's visibility through the marginal gingiva (reference test) has been considered a reliable criterion to describe a thin gingiva. This study aimed to evaluate in children two more convenient methods: the whitening of the attached gingiva with coronal labial traction (GW test) and the visibility of the gingival blood supply (BS test). Materials and Methods: In 69 children, the GT of primary and/or permanent central and lateral incisors, first primary molars and/or first premolars was assessed with the three tests. The sensitivity and specificity of the GW and BS tests and their odds ratio with probing were calculated. Results: According to probing, 39% of children in the studied population had thin gingiva. The GW and BS tests reported different percentages of GT compared to probing, except for primary teeth, maxillary permanent incisors and mandibular first premolars, where the GW test exhibited a comparable percentage. The sensitivity of GW and BS tests was 37% and 19%, respectively, when compared to probing, while the specificity was 84% and 96%, respectively. Conclusion: The GW and BS tests could be used for first-line diagnosis of thin gingiva; if the results are negative, probing should be implemented. Keywords: gingival biotype, gingival thickness, paediatric dentistry, prevention