In respiration, energy is released whereas in photosynthesis, energy is stored as carbohydrates.
In respiration, oxygen is used, carbon dioxide and water are released whereas in photosynthesis, carbon dioxide and water are used, oxygen is released.
Respiration involves the breaking of carbohydrates whereas photosynthesis involves the synthesis of carbohydrates.
Respiration results in a loss of dry mass whereas photosynthesis results in a gain of dry mass.
Respiration takes place all the time in all cells, with or without light whereas photosynthesis takes place only in cells containing chloroplasts, in the presence of light.