INTRODUCTION: The Holmium laser is the most used energy source in flexible ureterrenoscopy (URSf). The Lumenis Pulse 120H® laser has a higher system energy, a higher energy per pulse and a higher repetition frequency in relation to other types of lasers, which offers advantages in the treatment of lithiasis.OBJECTIVE: To analyze the results that we have obtai-ned with the use of the Lumenis Pulse120H® laser in patients treated by intrarenal retrograde surgery (RIRS). As secondary objectives there are: the study of the de-mographic variables of the patients, the characteristics of the stones and the complications associated with the procedure.MATERIAL AND METHODS: An observational, retros-pective study of the first 26 patients treated by RIRS and Lumenis Pulse 120H® laser has been performed in our Service between August 2018 and February 2019. The size of the lithiasis was measured on the simple ra-diography and the CT, in addition, the volume of the lithiasis was calculated. For the realization of RIRS, 8.5 Fr digital flexible ureterorenoscope (Olympus®) and the Holmium Lumenis 120H® laser with 200 micron laser fibers from Lumenis® were used. Statistical analysis was performed with the SPSSv21 system.RESULTS: A total of 26 patients with renal lithiasis have been analyzed. The median age was 55.15 years (40.67-67.05). 57.7% of the patients had prior surgical treatment of lithiasis. Thirteen patients presented the litia-sis in the renal pelvis, ten in the Upper Calicial Group (GCS), fifteen in the Middle Calicial Group (GCM) and eighteen in the Lower Calicial Group (GCI). The median of the lithiasic volume was 1826.41 mm3. Our overall success rate was 80.8% (100% success in lithiasis less than 2 cm and 85.7% in lithiasis between 2-3 cm). Five patients presented complications, of which 4 were Cla-vien II and 1 Clavien IIIb. No significant results were found between the lithiasic size and the presence of complications (p = 0.128).CONCLUSIONS: The use of the Lumenis Pulse 120H® laser is an useful tool for the treatment of kidney stones by RIRS, due to his efficiency in the fragmentation and dusting, taking into account that very large lithiasic mas-ses require, in a high percentage of cases, more than one treatment session.