Increasing housing demand and the precious value of city land have caused to the construction of multistorey, deep-plan and compact buildings. Architectural design needs to provide the appropriate penetration of daylight and ventilation into the deep-plan buildings. Therefore further researches are necessary in the field of natural lighting and ventilation systems. Light-well is an architectural daylight system to deep-plan building which is widely used in the residential buildings of the case study of this research (Tehran, Iran). In this study, effective factors in daylight performance of light-wells are investigated with dynamic daylight metrics. In this research, the continuous daylight autonomy (DAcon) is utilized for evaluating of annual illuminance for attached rooms to light-well. The main goal of this research is to estimate the effect of some affecting variables on the daylighting performance of light-wells (the area and horizontal section form, the optimal height of the light-well, orientation variation and the slope of light-well surrounding wall) to provide suggestions for better utilization of light-wells in residential building. 352 computer simulations using Daysim software have been conducted to assess the expressed variables. Also, Autodesk Ecotect software has been used as graphical user interfaces for Daysim. The findings of this study show the better daylighting performance of cylindrical light-wells compared with the common square light-well in Tehran. Also, the optimal height of different types of light-wells in residential buildings has been suggested with regards to the adequate daylight autonomy (DA) in connected rooms to light-well. The results of this study show that the increasing of the suggested optimal height for different types of light-wells is possible with increasing the slop of walls of light-wells and the window size in the lower floors. (C) 2017 Elsevier Ltd. All rights reserved.