A diagnostic information display system for a construction machine includes a sensor for detecting status variables related to an operating state of a hydraulic excavator or ambient environment, and a controller which stores combinations between a plurality of snapshot items and one or more status variables related to each of the snapshot items in advance, acquires or extracts status variable data, which is regarded as being related based on the stored combinations, from corresponding detected signals of the sensor 40, etc. with respect to the snapshot item selected by a selection command from an operator, thereby displaying the status variable data on a display unit, and compares each of the status variables or a value computed based on a plurality of status variables with a predetermined reference value range. A failure of a corresponding part or the related status variable is displayed on the display unit.