Background To plan craniospinal irradiation (CSI) with ‘‘field-in-field’’ (FIF) homogenization technique in combination with daily, intra-fractional modulation of the field junctions, to minimize the possibility of spinal cord overdose. Photon-based techniques for CSI may result in dose inhomogeneity within the treatment volume and usually require a weekly manual shift of the field junctions to minimize the possibility of spinal cord overdose. Nowadays FIF technique is used to feather out the dose inhomogeneity caused by multiple fields. We have started using this technique after acquiring advanced technology machines in recent years. Methods and Materials: 16 patients treated with 3D-CRT for CSI were retrospectively chosen for analysis. These patients were treated during 2016–2017. Contouring of PTV and OAR were done and planning done on Eclipse TM TPS (Varian). These patients were planned with Lateral cranio-cervical fields and posterior spinal fields using a forward-planned, FIF technique. Field junctions were automatically modulated and custom-weighted for maximal homogeneity within each treatment fraction. Dose volume histogram (DVH) was used for analysis of results. A corresponding plan without FIF technique was planned and maximum dose at the junction was noted for each patient with both plans and the readings were evaluated. Results Plan inhomogeneity improved with FIF technique. It provided consistent dose delivery during each fraction of treatment across the junctions. The maximum doses calculated at the junction were higher in the CSI plans without FIF compared to those with FIF technique. Conclusion This paper hence proves that FIF technique is better in planning CSI.