This study investigates and analyses the possibility of cyanobacteria bloom detection as a case study in the Gulf of Finlandand southern Finish lakes. The results show that MODIS data are difficult to be used in cyanobacteria bloom early warning. The mainreason is that MODIS data are more suitable for CASE I waters as there are five bands in the spectral region of 400-550nm. However,for CASE II waters (estuary, coastal, and lakes), the maxima of reflectance spectra are shifting towards longer wavelengths withincreasing turbidity or increasing amount of CDOM. This suggests that the reflectance maximum in coastal waters often occurs in thespectral range of 550-670nm where MODIS data do not have any spectral bands. In contrast, MERIS data have three bands of 560,620, and 665nm at the spectral region of 550-670nm. The two bands at 620nm and 665nm are potentially important bands ofdetecting cyanobacteria bloom of the coastal waters (and/or lakes). The reason is that there are the phycocyanin absorption near630nm and a reflectance peak near 650nm. In fact, MODIS and MERIS data are unlikely applicable to warn potentially cyanobacteriabloom in its early stages, but able to monitor the already formed blooms. This methodology of satellite-based observations can beapplied to detection and monitoring of cyanobacteria bloom in Lake Taihu and coastal regions of China.