Abdominal free air upon X-ray examination implies a medical emergency, but there is an extensive differential diagnosis that should be considered. Fecaloma is one of the possible imitators of free abdominal air. Fecaloma is a complication of chronic constipation, in which a large fecal mass impacts the bowel, imitating a tumor mass. This phenomenon is not uncommon in the elderly, and requires prompt recognition and immediate medical treatment. A 29-year-old woman, known to suffer from mental retardation, was admitted due to frequent vomiting and diarrhea following constipation a few days prior to her admission. The patient was treated in her institution by an enema, with partial decompression, that was followed by recurrent vomiting and fever. Physical examination upon admittance revealed a distended abdomen without peritoneal signs. An abdominal X-ray series demonstrated a distended large bowel with an abundance of fecal contents, and suspected free air in the abdominal cavity. Due to these findings, an abdominal CT was performed, which demonstrated a huge fecaloma involving the descending and sigmoid colon. The patient was treated non-operatively with: IV fluids, oral laxatives, frequent enemas and manual stool disimpaction. Following this treatment the patient's condition improved dramatically. Fecaloma is a situation that requires prompt recognition and treatment. The diagnosis of fecaloma is a clinical challenge. In addition to signs, symptoms and physical examination, which may be non-specific, the use of X-rays, CT and US may aid in the diagnosis. The treatment in most cases consists primarily of hydration, laxatives, enemas and manual disimpaction. If there is no improvement, one should consider endoscopic treatment, or surgery which may entail a partial or total colectomy.