Diabetes and Nephrotic syndrome (NS) promote plaque-related gingivitis and yeast-like fungal infections. The study assesses the impact of Candida spp. and general disease- or treatment-related factors on plaque-related gingivitis severity in children and adolescents with Nephrotic syndrome /diabetes. Body mass index (BMI), BMI standard deviation score, and oral cavity (Plaque Index--PLI, Gingival Index--GI, mucosa status, presence and Candida enzymatic activity) were assessed in 96 patients (32 with NS: 30- immunosuppressive treatment, 35--type 1 diabetes, and 29 generally healthy), aged; 3-18 years. Laboratory included cholesterol and triglyceride measurements; in diabetic subjects- glycated haemoglobin, in NS: total protein, albumin, creatinine, haemoglobin, haematocrit, white cell count, urinary protein excretion. Medical records supplied information on disease duration and treatment. A statistical analysis was performed; Kendall Tau coefficient, chi-square test, t-test, and multiple regression analysis ( P < 0.05). Candida spp. often occurred in healthy patients, but oral candidiasis was found only in the NS and diabetes groups (9.37% and 11.43%). Gingivitis occurred more frequently in patients with NS/diabetes. Gingivitis severity was correlated with PLI, age, and yeast enzyme activity in NS--to with immunosuppressive treatment with >1 drug, drug doses, treatment duration, lipid disorders, and BMI; in diabetes, with blood glucose and glycated haemoglobin >8%. Poor hygiene control is the main cause of gingivitis. Gingivitis severity is most likely related to age, lipid disorders and increase in body mass. Candida spp., in uncompensated diabetes and in those using immunosuppressive treatment, might intensify plaque-related gingivitis.