This paper attempts to identify the sources and evaluate the prevalence of halitosis in children with adenoid hypertrophy. The study included pediatric patients admitted for adenoidectomy due to obstructive symptoms. Patients with possibly other causes of halitosis, were excluded from the study. Halitosis was detected in 30 out of 136 children (22.1%). The effect of adenoid hypertrophy on halitosis was confirmed by the significant reduction in the organoleptic score rated according to the Rosenberg scale (on average by 2°) and the levels of volatile sulfur compounds (on average 84 ppb) post-adenoidectomy, as compared to pre-surgery results. In total, we reported a statistically significant decrease in the abovementioned values in 90% of patients with halitosis. It was found that in patients with halitosis, as compared to patients with no oral malodor, anaerobic bacteria and Staphylococcus aureus were more frequently observed in the adenoid tissue. Streptococcus oralis strains were more commonly reported in the material taken during adenoidectomy in children without oral malodor.