Processes for preparing amidoamine products derived from hydrocarbon polymers containing carboxylic acid, thioacid, ester or thioester functional groups are disclosed. More particularly, a process is disclosed which comprises the steps of: (A) reacting (i) a hydrocarbon polymer functionalized to contain functional groups of formula --CO--Y--R.sup.3, the hydrocarbon polymer having a number average molecular weight of at least about 500 prior to functionalization, wherein Y is O or S, R.sup.3 is hydrogen, hydrocarbyl, or substituted hydrocarbyl and wherein at least 50 mole % of the functional groups are attached to a tertiary carbon atom of the polymer, with (ii) a volatile amine containing at least two reactive amino groups under conditions effective to amidate at least a portion of the --CO--Y--R.sup.3 functional groups and form a first amidoamine adduct containing at least one reactive amino group; and (B) reacting the first amidoamine adduct with an .alpha.,.beta.-unsaturated compound to form a second amidoamine adduct, wherein the .alpha.,.beta.-unsaturated compound has the formula: ##STR1## wherein X is O or S; Z is OR.sup.7, --SR.sup.7, or --NR.sup.7 (R.sup.8); and R.sup.4, R.sup.5, R.sup.6, R.sup.7 and R.sup.8 are the same or different and are hydrogen, hydrocarbyl, or substituted hydrocarbyl. In reaction step (B), the reactive amino groups in the first amidoamine adducts react non-selectively with both the carbon--carbon double bonds and the --C(.dbd.X)Z functional groups in the unsaturated compounds or, with suitable control of the reaction conditions, react selectively with the carbon--carbon double bonds only. In the case of selective reaction, the second amidoamine adduct is characterized by having unreacted --C(.dbd.X)Z functional groups, and the adduct can be further reacted with a second amine in order to amidate the --C(.dbd.X)Z functional groups. The amidoamine products are useful as additives in fuels and lubricating oils.