The study presents an experimental analysis of gas-liquid flow pattern - gas holdup intercorrelation in two bubble columns with inner diameter of 0.04 m and 0.10 m respectively, using now visualization the joint analysis of the wall pressure fluctuation, the residence time distribution of liquid phase and gas holdup measurements. In these small bubble columns, different flow regimes dependent on the different parameters are developed: process (gas and liquid superficial velocities), material (liquid phase rheological behaviour) and geometrical (column diameter, H/D-c ratio, sparger design). The flow pattern and gas holdup influence each other and are strongly dependent on these parameters. Also, the flow configurations and gas holdup behaviour were analysed in connection with the existing patterns and with some correlations available in literature.