This paper addresses the design of CMOS thermal accelerometers. A test-chip including the sensor and a signal conditioning circuit has been designed, fabricated and characterized. The fabricated prototype exhibits good performances: the measured resolution is better than 30mg (equivalent to 1.7° in inclination) with a sensitivity of 375mV/g. The bandwidth is around 15Hz. This test-chip is used to improve the modelling of heat transfer phenomenon for this family of devices. FEM is successfully used as a first modelling approach. Although thermal convective accelerometers have already been reported and even commercialised, few information regarding behavioural modelling, optimization issues, and their integration on CMOS technology is today available. In particular, no information about response time modelling was reported in the literature. Thanks to experimental results and FEM simulations, we provide in this study information concerning the integration of convection heat transfer accelerometers on CMOS. In addition, the effects of the packaging (i.e. the top and bottom cavities) on both the static sensitivity and the dynamic response of the sensor have been investigated.