The helium hydride ion has six relatively stable isotopologues, that differ in the isotopes of the two elements, and hence in the total atomic mass number (A) and the total number of neutrons (N) in the two nuclei:
*  or  (A = 4, N = 1) 
*  or  (A = 5, N = 2) 
*  or  (A = 6, N = 3; radioactive) 
*  or  (A = 5, N = 2) 
*  or  (A = 6, N = 3) 
*  or  (A = 7, N = 4; radioactive) 
They all have three protons and two electrons.  The first three are generated by radioactive decay of tritium in the molecules HT = , DT = , and  = , respectively.  The last three can be generated by ionizing the appropriate isotopologue of  in the presence of helium-4.
The following isotopologues of the helium hydride ion, of the dihydrogen ion , and of the trihydrogen ion  have the same total atomic mass number A:
* , , ,  (A = 4)
* , , , ,  (A = 5)
* , , , ,  (A = 6)
* , ,  (A = 7)
The masses in each row above are not equal, though, because the binding energies in the nuclei are different.