Many olfactory cues pervade the aquatic environment of fish and induce various behaviors important for their survival and species preservation, such as searching foods, escaping from danger, and finding potential mates. Zebrafish has become one of the most useful model organisms in neurobiology. In addition to its general advantageous properties (external fertilization, rapid development, transparency of embryos, etc.), zebrafish is amenable to various genetic engineering technologies such as transgenesis, mutagenesis, gene knockdown/knockout, and transposon-mediated gene transfer. Our transgenic approach unraveled two segregated neural pathways originating from ciliated and microvillous sensory neurons in the olfactory epithelium to distinct regions of the olfactory bulb. Furthermore, the two basic principles, one neuron - one receptor rule and axon convergence to target glomeruli, are essentially preserved also in zebrafish, rendering this organism a suitable model vertebrate for the olfactory research. In this lecture, I will summarize advances in our knowledge on the functional architecture of the olfactory neural circuits in zebrafish, which mediate specific odor-induced behaviors. In particular, I will focus on molecular genetic dissection of the neural elements involved in the attraction to food odors, the aversion from alarm pheromone, and the social response to sex pheromones.