Introduction Lung ultrasound findings in infants and children are similar to those described in adults.

Despite ultrasound screening avoids the use of ionising radiation, the interest of specialists toward lung ultrasound examinations is still scarce.

Aims To compare lung ultrasounds with chest X-ray imagines for diagnosis of pneumonia and pleural effusion and to evaluate the ultrasound pattern in patients with Mycoplasma Pneumoniae infection.

Materials and methods Forty children (mean age 4.2 yr, 21 females), admitted in the paediatric ward for respiratory tract infections, underwent chest X- ray, lung ultrasound examination and serum sample for Mycoplasma Pneumoniae. Presence of ultrasound B-lines was accepted as a signal of interstitial involvement.

Results Chest X-ray and ultrasound examination yielded concordat results for pneumonia and/or pleural effusion in 29/40 (72,5%) patients. In addition, ultrasounds detected pleural effusion in 10 patients, not revealed by chest X-ray imagines.

Ultrasound B-lines were found in 5/8 (62.5%) Mycoplasma-positive in contrast with only 7/32 (21,8%) Mycoplasma-negative patients (p < 0.05).

Conclusions Lung ultrasound examination is safe, can be performed repeatedly and complement chest X-ray for assessing pneumonia and pleural effusion in infants and children. An ultrasound pattern with increased B-line could be useful to assess interstitial involvement by Mycoplasma infection.