Method for operating an exhaust-gas aftertreatment system of an internal combustion engine, which exhaust-gas aftertreatment system has an exhaust-gas line for conducting an exhaust-gas mass flow and has an SCR particle filter arranged in the exhaust-gas line , wherein a device for targeted, defined variation of the NH 3 and/or NO x concentration is arranged in the exhaust-gas mass flow upstream of the SCR particle filter , and at least one first concentration sensor is arranged in the exhaust-gas mass flow downstream of the SCR particle filter , in order to detect apertures in the filter substrate of the SCR particle filter , having the following steps: - setting the internal combustion engine to a diagnostic operating mode, wherein certain relevant diagnostic operating parameters (D-BP) of the internal combustion engine are verified for, or set or adjusted to, correspondence with diagnostic default values (D-BP_set); in the presence of the diagnostic operating mode, - targeted, defined inducement of an NH 3 concentration change and/or of an NO x concentration change in the exhaust-gas mass flow upstream of the SCR particle filter in relation to the values of the NH 3 concentration and/or of the NO x concentration that are present in the diagnostic operating mode; - measuring the NH 3 and/or NO x concentration change in the exhaust-gas mass flow downstream of the SCR particle filter within a specified time window (TW), which directly follows the abovementioned NH 3 and/or NO x concentration change measured upstream of the SCR particle filter , by means of the at least one first concentration sensor , which outputs a corresponding first concentration measurement signal ; and - providing a correlating concentration comparison value (VgW) at least on the basis of the first concentration measurement signal ; - evaluating the NH 3 and/or NO x concentration change downstream of the SCR particle filter measured within the specified time window (TW) on the basis of the respective concentration comparison value (VgW) and predefined limit values (GW); and - diagnosing the SCR particle filter as defective owing to apertures in the filter substrate if the evaluation yields that the concentration comparison value (VgW) has overshot at least one predefined limit value (GW) . - setting the internal combustion engine to a diagnostic operating mode, wherein certain relevant diagnostic operating parameters (D-BP) of the internal combustion engine are verified for, or set or adjusted to, correspondence with diagnostic default values (D-BP_set); in the presence of the diagnostic operating mode, - targeted, defined inducement of an NH 3 concentration change and/or of an NO x concentration change in the exhaust-gas mass flow upstream of the SCR particle filter in relation to the values of the NH 3 concentration and/or of the NO x concentration that are present in the diagnostic operating mode; - measuring the NH 3 and/or NO x concentration change in the exhaust-gas mass flow downstream of the SCR particle filter within a specified time window (TW), which directly follows the abovementioned NH 3 and/or NO x concentration change measured upstream of the SCR particle filter , by means of the at least one first concentration sensor , which outputs a corresponding first concentration measurement signal ; and - providing a correlating concentration comparison value (VgW) at least on the basis of the first concentration measurement signal ; - evaluating the NH 3 and/or NO x concentration change downstream of the SCR particle filter measured within the specified time window (TW) on the basis of the respective concentration comparison value (VgW) and predefined limit values (GW); and - diagnosing the SCR particle filter as defective owing to apertures in the filter substrate if the evaluation yields that the concentration comparison value (VgW) has overshot at least one predefined limit value (GW) . <EOS>