In the present work, nanoflower-shape zinc oxide (ZnO) films synthesized by modified chemical bath deposition (CBD). The optimum working temperature and pH was determined 50 +/- 5 degrees C and 9.8, respectively. Conditioning solution can functioned as an adhesive in CBD process which have been used for the first time. The effect of annealing temperature (450, 500 and 550 degrees C) was studied and the changing structural, elemental and morphological properties were investigated by using XRD, EDX and SEM devices, respectively. All polycrystalline films had  preferential orientation and the maximum crystallization was observed in ZnO films that annealed at 500 degrees C. Detailed optical properties (absorption, band gap energy) were investigated by using Uv-Vis spectroscopy. Optical transmittance spectra showed high optical absorption below to 370 nm in the range 300-900 nm. Gas sensing mechanism for 0.5 ppm NO2 gas was investigated by using home-made gas sensing chamber that sensor working at 200 degrees C and nano-flower dimensions severly affected to gas sensitivities.